Wet  VAlls  and 

Efflorescence 


What  Efflorescence  is 
and  How  to  Avoid  It 


H.  D.  Stewart  Co. 

505  HILLS  BUILDING 
SYRACUSE,  N.  Y. 


AVERY  U:V.SV 

Digitized  by.thednteffiet  Archive 
in  2020  with  funding  from 
Columbia  University  Libraries 


https://archive.org/details/wetwallseffloresOOpalm 


Wet  Walls  and 
Efflorescence 


What  efflorescence  is  and  how 
to  avoid  it,  with  examples 
showing  the  results  of  neglect 


By  L.  A.  Palmer,  Research  Associate 

Results  of  two  investigations  conducted  at  the 
National  Bureau  of  Standards,  U.  S.  Department 
of  Commerce,  Washington,  D.  C.,  George  K. 
Burgess,  Director 


AMERICAN  FACE  BRICK  ASSOCIATION 
130  North  Wells  Street,  Chicago 


NINETEEN  TWENTWEIGHT 


TABLE  OF  CONTENTS 


Summary  of  Results  ------ 

Gives  in  brief  the  most  important  features  of 
the  two  investigations. 


Wet  Walls  and  Efflorescence 

Part  I.  Certain  Fundamental  Principles  - 

Includes  an  analysis  of  the  conditions  under 
which  efflorescence  occurs,  and  shows  two 
drawings  illustrating  the  right  and  wrong  pro- 
files  for  a  coping. 


Part  II.  Field  Work  -  -  -  -  - 

Includes  53  photographic  illustrations,  with  a 
detailed  analysis  of  the  causes  of  efflorescence 
and  possible  means  of  preventing  it,  in  the 
case  of  each  building  shown. 


Efflorescence  on  Face  Brick  Walls  - 

Reports  the  results  of  a  study  regarding  the 
occurrence  of  efflorescence-producing  mate¬ 
rials  in  brick  and  mortar,  and  explains  how 
mortar  may  be  made  water-repellent. 


SUMMARY  OF  RESULTS 


Efflorescence  may 

occur  upon  the  surface 
of  any  masonry  wall  as  a 
whitish  deposit.  Whenever 
such  efflorescence  appears,  it 
means  that  the  wall  contained 
both  soluble  salts- — usually 
calcium  and  magnesium  sub 
fates — and  moisture. 

These  soluble  salts  may 
have  been  in  any  or  all  of  the 
masonry  materials  used  in 
the  wall,  in  facing,  backup  or 
mortar.  The  moisture  may 
have  entered  the  wall  during 
construction,  through  expo¬ 
sure  to  rain  or  snow.  It  may 
have  penetrated  from  the 
earth  at  the  base  or  from  im¬ 
properly  flashed  parapet 
walls  at  the  roof.  It  may  have 
come  from  leaky  gutters  and 
downspouts,  or  from  the  lack 
of  drips  on  cornices  and  sills. 

It  may  have  entered  through 
poorly  filled  or  cracked 
mortar  joints  in  the  wall. 

Once  in  the  wall,  the  moisture  dissolves  some  of  the  salts 
present,  and  later  passes  to  the  surface  when  conditions 
become  favorable  for  evaporation.  Then,  when  evapora¬ 
tion  takes  place,  the  salts  are  left  behind  on  the  wall  as 
efflorescence.  No  masonry  material  is  always  exempt  from 
contributing  to  the  development  of  noticeable  efflorescence, 
but  some  materials  contain  much  larger  quantities  of  soluble 
salts  than  others,  and  consequently  are  much  more  im¬ 
portant  sources  of  trouble. 

Prevention  of  efflorescence  must  begin  with  the  design 
of  the  building,  follow  through  the  selection  of  materials 
and  the  methods  of  work  during  the  construction  period, 
and  continue  with  maintenance  of  the  structure  after  its 
completion.  However,  the  methods  recommended  and  the 
precautions  necessary  are  merely  those  of  good  practice  and 
do  not  involve  radical  departures  from  recognized  standards 
except  possibly  in  the  case  of  adding  a  water-repellent  to 
the  mortar.  But  the  neglect  of  certain  simple  precautions 
may  bring  very  unsatisfactory  results. 

Wet  walls  serious  fault 

The  great  importance  of  excluding  moisture  from  the 
wall  is  brought  out  in  Part  I  of  the  report  on  “Wet  Walls 
and  Efflorescence,”  as  follows  (page  8): 

“Aside  from  being  the  direct  cause  of  efflorescence,  an 
excessive  amount  of  moisture  in  the  materials  of  a  wall 
accelerates  disintegration  of  such  materials  through  alter¬ 


nate  freezing  and  thawing 
of  this  moisture  in  the  wall. 
Damp  interiors  are  often 
another  undesirable  condi¬ 
tion  attending  the  disinte¬ 
gration  and  occurrence  of 
efflorescence.  It  is  therefore 
seen  that  a  study  of  efflores¬ 
cence  from  the  standpoint  of 
proper  design,  construction 
and  maintenance  must  of 
necessity  involve  also  certain 
phases  of  the  study  of  both 
disintegration  of  materials  in 
walls  and  damp  interiors. 
This  is  the  most  important 
reason  for  making  a  concen¬ 
trated  effort  in  all  future 
construction  to  make  and 
preserve  dry  walls.” 

Note  that  disintegration 
and  damp  interiors  are  only 
attendant  circumstances. 
They  are  not  consequences 
of  efflorescence.  The  alter¬ 
nate  freezing  and  thawing  of 
moisture  disrupts  masonry 
and  this  happens  whether  or  not  there  are  any  salts  present 
in  such  masonry.  The  report  continues: 

“In  view  of  such  facts  the  manufacturers  of  face  brick 
are  at  present  outlining  a  future  study  of  a  great  many 
of  the  factors  involved  in  creating  and  maintaining  the 
best  possible  conditions  for  their  material  in  the  walls 
where  they  are  to  be  used.  Obviously,  since  face  brick 
must  be  used  with  many  other  materials  in  such  walls, 
such  a  study  involves  not  only  the  building  units,  brick, 
but  also  assemblages  of  units  of  brick  together  with  units 
of  various  other  materials. 

“In  the  investigation  of  causes  of  and  remedies  for 
efflorescence  on  face  brick  walls  (page  24),  it  developed 
that  the  soluble  salts  that  would  otherwise  be  present  in 
clay  products  used  in  construction  can  be  practically 
eliminated  by  the  manufacturer  of  such  materials  by  certain 
procedures  in  the  drying  and  burning  of  his  ware,  together 
with  the  judicious  use  of  barium  compounds  in  his  clay. 
These  procedures  are  at  present  being  generally  used  by 
the  face  brick  industry  and  in  part  justify  the  difference  in 
cost  between  face  brick  and  the  cheaper  clay  products, 
hollow  tile  and  common  brick  used  generally  as  backing  up 
materials.  From  an  economic  standpoint,  it  is  not  always 
practicable  for  the  manufacturers  of  common  brick  and 
hollow  tile  to  adopt  the  procedures  used  by  the  face  brick 
industry  in  eliminating  soluble  salts.  From  the  standpoint 
of  efflorescence  it  is  therefore  very  essential  that  these  back- 


This  summary  has  been  prepared  by  the 
American  Face  Bricfi  Association  to  present  as 
briefly  as  possible  the  outstanding  facts  about 
the  occurrence  of  efflorescence  on  masonry  walls 
and  how  to  avoid  it,  as  determined  by  two 
investigations  conducted  for  the  Association  at 
the  Rational  Bureau  of  Standards,  U.  S. 
Department  of  Commerce,  Washington,  D.  C. 
It  is  of  course  impossible  to  treat  this  subject 
adequately  in  a  summary,  and  there  is  no 
doubt  that  the  short  time  needed  to  read  the 
complete  reports  which  follow  will  be  most 
profitably  spent.  The  55  illustrations,  occur' 
ring  chiefly  in  Part  II  of  the  first  report,  will  be 
found  especially  interesting.  The  investiga' 
tions  described  were  carried  on  by  L.  A. 
Palmer,  Research  Associate,  under  George  K. 
Burgess,  Director  of  the  Bureau  of  Standards, 
and  the  Research  Committee  of  the  American 
Face  Bric\  Association,  composed  of  F.  W. 
Butterworth,  Chairman,  Wm.  C.  Koch  and 
L.  B.  Rainey.  For  additional  copies  of  this 
boofi,  write  the  American  Face  Bric\  Associa' 
tion,  130  Tforth  Wells  Street,  Chicago. 


6 


WET  WALLS  AND 

ing  up  materials  be  protected  from  excessive  water  pene- 
tration.  These  efforts  on  the  part  of  face  brick  manufac- 
turers  to  reduce  the  amount  of  salts  in  their  own  product 
will  not  alone  suffice  in  eliminating  efflorescence.” 

Occurrence  of  soluble  salts 

In  the  investigations  at  the  Bureau  of  Standards,  55  types 
of  face  brick  from  as  many  different  manufacturers  in  vari¬ 
ous  parts  of  the  United  States  were  examined  for  soluble 
salts.  Six  types  of  common  brick  and  four  each  of  widely 
used  limes,  portland  cements  and  bricklayers’  cements  were 
also  studied.  The  majority  of  the  face  brick  contained  less 
than  0.05  per  cent  of  soluble  sulfuric  anhydride  (taken  as 
the  chemist’s  guide  to  the  soluble  salts  present).  This 
amount  is  ordinarily  insufficient  to  cause  efflorescence  even 
under  conditions  favorable  for  its  development. 

Each  sample  of  common  brick  exceeded  this  amount  and 
the  average  of  all  six  types  was  0.16  per  cent.  The  lowest 
figure  for  the  limes  was  0.5  per  cent.  The  portland  cements 
and  bricklayers’  cements  also  contained  varying  quantities 
of  these  salts,  and  in  the  tests  reported  under  “Efflorescence 
on  Face  Brick  Walls,”  page  24,  each  was  found  to  develop 
efflorescence  when  used  in  certain  panels  with  face  brick 
which  alone — that  is,  tested  without  mortar — did  not 
develop  efflorescence.  Other  investigations  of  limes  and 
building  limestones  have  established  the  presence  in  these 
materials  of  the  same  soluble  salts  found  in  brick. 

In  testing  brick  for  soluble  salts,  the  sample  for  analysis 
need  not  include  any  material  taken  from  more  than  one- 
eighth  of  an  inch  below  the  exposed  surface  of  the  brick,  as 
the  amount  of  such  salts  is  usually  greatest  there.  (Bureau 
of  Standards  Technologic  Paper  No.  370,  page  617.) 

Maying  rnortar  water-repellent 

Since  water  ordinarily  penetrates  into  a  wall  through  the 
mortar  joints  rather  than  through  the  brick  or  stone,  care¬ 
ful  study  was  given  to  methods  of  making  the  mortar 
water-repellent.  The  plan  recommended  is  the  addition  of 
two  per  cent  by  weight  of  calcium  or  ammonium  stearate 
to  the  cement,  lime  or  mixture  of  the  two  used  in  the 
mortar.  Mortars  so  treated  were  found  to  be  very  effective 
in  preventing  the  passage  of  moisture  in  all  cases  wherein 
only  ordinary  capillary  forces  obtain.  While  best  practice 
would  call  for  the  use  of  stearate  in  mortar  for  backing  as 
well  as  facing  materials,  it  is  especially  important  that  it  be 
employed  in  laying  up  the  facing  where  the  joints  will  be 
subjected  to  unusual  exposure  to  driving  rains  or  to  water 
running  down  the  surface  of  the  wall.  Joints  of  copings, 
window  sills  and  parapet  walls  are  all  in  need  of  especial 
care.  In  repointing  joints  that  have  cracked,  water-repel¬ 
lent  mortar  is  called  for,  as  such  joints  are  usually  in  highly 
exposed  locations. 

Calcium  stearate  is  a  powder  which  is  mixed  dry  with 
the  cement  before  adding  sand  and  water,  while  ammonium 
stearate  is  a  paste  which  is  usually  added  to  the  mixing 
water.  On  the  ordinary  building  job,  the  powder  has 
proved  the  more  practical  and  accurate  to  use  with  the 
equipment  commonly  available.  These  stearates  can  be 


EFFLORESCENCE 

obtained  from  chemical  manufacturers,  or  integral  water¬ 
proofing  compounds  containing  them  can  be  had  through 
dealers  in  building  supplies  and  branch  offices  of  companies 
making  such  products.  Every  care  should  be  taken  to 
insure  getting  reliable  material,  and  unless  the  particular 
product  being  considered  is  known  to  be  satisfactory,  it 
should  be  given  suitable  laboratory  tests. 

For  addresses  of  manufacturers  of  stearates  and  integral 
waterproofing  compounds  containing  them,  write  the 
American  Face  Brick  Association,  130  N.  Wells  St.,  Chicago. 

Other  precautions  for  peeping  walls  dry 

Specific  recommendations  that  will  help  in  preventing 
water  from  entering  the  wall  are  as  follows :  Use  imper¬ 
vious  copings,  and  point  joints  carefully  with  water-repellent 
mortar.  Flash  parapet  walls,  carrying  the  flashing  com¬ 
pletely  through  the  wall  one  or  two  courses  above  the 
roof  level,  and  waterproof  the  entire  inner  side  of  the  wall. 
Likewise  flash  the  washes  of  pediments  and  dormers. 

Always  provide  adequate  drips  on  all  copings,  cornices 
and  window  sills,  making  the  grooves  at  least  jbs  inch  wide 
and  inch  deep,  and  provide  projections  of  two  inches 
or  more  so  as  to  keep  the  drip  away  from  the  wall. 

Use  lug  sills  at  windows,  with  slopes  from  the  sides  of 
the  window  to  the  opening  and  at  right  angles  to  the  wall, 
and  where  practical  avoid  all  joints  in  the  sills.  If  brick 
sills  are  desired,  flash  under  them  with  suitable  metal 
flashing  provided  with  drips.  Employ  projecting  rows  of 
brick  very  cautiously,  and  use  water-repellent  mortar  for 
the  joints  beneath  them.  Avoid  vertical  joints  in  any  sort 
of  masonry  wherever  possible,  and  be  sure  water-repellent 
mortar  is  employed  in  such  joints. 

Protect  walls  under  construction  to  prevent  rain  or 
melting  snow  from  entering.  Pile  brick,  tile,  stone  and 
similar  materials  on  boards  as  delivered  to  the  job  to  avoid 
contact  with  moist  ground,  and  keep  them  covered.  Keep 
gutters  and  downspouts  in  good  repair,  and  make  sure  they 
are  adequate  to  carry  the  water.  Point  up  cracked  joints 
very  promptly.  Coat  the  backs  of  retaining  walls  with  an 
impervious  layer,  and  keep  brick  building  walls  away  from 
contact  with  the  earth. 

Classification  of  various  types  of  efflorescence 

While  efflorescence  is  most  common  in  the  early  spring, 
when  walls  saturated  by  melting  snow  or  late  winter  rains 
are  drying  out,  it  may  occur  at  any  time  of  the  year.  It 
may  appear  quite  generally  over  a  wall,  or  be  confined  to 
certain  small  areas.  Analysis  shows  there  are  these  four 
conceivable  conditions  under  which  efflorescence  may  occur : 

Condition  A.  Excessive  water  with  only  a  normal 
amount  of  salts  in  the  wall. 

Condition  B.  Excessive  water  and  an  excessive  amount 
of  salts  in  the  wall. 

Condition  C.  Normal  water  and  normal  salts. 

Condition  D.  Normal  water  but  excessive  salts. 

Obviously  the  first  two  conditions,  A  and  B,  are  the 
worst  because  disintegration  may  go  hand  in  hand  with 


WET  WALLS  AND 


EFFLORESCENCE 


7 


efflorescence,  owing  to  the  disruptive  action  of  freezing 
and  thawing.  Condition  B  is  of  course  worse  than  A. 

Efflorescence  occurring  under  Condition  C  is  usually 
very  mild,  indeed.  Condition  D  may  cause  some  trouble, 
but  like  C,  is  usually  only  temporary  and  tends  to  disappear 
entirely  as  time  goes  on. 

General  efflorescence  is  apt  to  mean  either  condition  B 
or  D,  where  the  wall  contains  excessive  salts.  Special 
efflorescence  usually  indicates  Condition  A,  characterized 
by  excessive  water  which  is  being  allowed  to  penetrate  the 
wall  by  some  fault  in  design,  construction  or  maintenance. 
Every  instance  of  a  leaking  downspout,  dripless  sill  or  urn 
flashed  parapet  wall  may  cause  excessive  water  penetration. 

Field  study  shows  efflorescence  preventable 

As  part  of  the  field  investigation  of  efflorescence,  William 
C.  Koch,  of  the  Research  Committee  of  the  American  Face 
Brick  Association  made  an  extensive  study  for  the  purpose 
of  correlating  the  fundamental  facts  about  the  development 
of  efflorescence  with  design,  construction  and  maintenance 
of  buildings.  Finally,  a  detailed  study  was  made  of  250  cases 
of  efflorescence  and  the  usual  accompaniment,  wall  disinte- 
gration.  The  Bureau  of  Standards  report  comments  as  follows : 

“With  but  one  or  two  definite  exceptions,  the  250  cases 
of  discoloration  and  disintegration  could  have  been  pre- 
vented  by  either  proper  design,  construction  or  mainte- 
nance.  In  some  cases  only  one  of  these  three  factors  was 
the  direct  cause,  but  usually  there  were  two  and  in  a 
number  of  cases  all  three  were  at  fault. 

“Efflorescence  was  observed  on  almost  every  type  of 
building  material ...” 

In  emphasizing  the  necessity  of  promptly  pointing  up 
cracked  mortar  joints  which  are  allowing  penetration  of 
water,  the  report  says: 

“Where  prompt  pointing  up  was  not  done  and  where  the 
condition  had  lasted  over  a  period  of  years,  disintegration 
of  the  mortar  joints  almost  invariably  had  occurred.  In 
any  case  where  underburned  brick  had  been  used,  these 
also  had  become  disintegrated.” 

The  action  of  sulfur  dioxide  in  accelerating  the  disinte- 
gration  of  certain  masonry  materials  is  well  known,  and 
must  be  considered  in  cities  burning  bituminous  coal. 
Snow  water  may  be  sufficiently  acid  to  attack  the  lime  of 
mortar  or  certain  limestones,  but  tests  made  at  the  Bureau 
of  Standards  have  shown  face  brick  highly  resistant  to 
solutions  of  sulfur  dioxide  in  water  and  even  to  fairly  com 
centrated  acid  solutions,  such  as  ten  per  cent  hydrochloric, 
sulfuric  and  nitric  acid.  However,  the  need  of  prompt 
pointing  up  of  mortar  joints  is  apparent. 

Recapitulation  of  results  of  investigation 

As  summing  up  the  results  of  the  entire  study  of 
efflorescence  on  masonry  walls,  the  following  recapitula- 
tion  of  his  report  by  L.  A.  Palmer  is  worthy  of  careful 
attention  (page  24): 

“The  purpose  of  the  foregoing  is  to  point  out  the 


fact  that  in  the  main,  the  immediate  cause  of  efflorescence 
and  often  too  of  wall  disintegration  is  excessive  penetration 
of  moisture  into  the  wall.  The  field  work  supplemented 
the  fundamental  work  that  had  already  been  done  and 
that  had  established  the  fact  that  hardly  any  masonry 
material  is  exempt  from  the  possibility  of  containing 
soluble  salts  in  quantity  such  that  it  may  under  favorable 
conditions  contribute  to  the  development  of  noticeable 
efflorescence.  The  favorable  conditions  are  wet  walls. 

“With  but  one  or  two  definite  exceptions,  all  of  the 
large  number  of  instances  of  efflorescence  and  in  some 
cases  wall  disintegration  that  were  studied  could  have 
been  prevented  had  due  consideration  and  care  been  given 
to  the  proper  design,  construction  and  maintenance  of 
these  buildings. 

“A  few  examples  of  such  preventable  instances  of 
efflorescence  have  been  shown.  Some  details  in  way  of 
design,  construction  and  maintenance  which,  had  they 
been  observed  and  remedied,  would  have  prevented  the 
occurrences  of  efflorescence  as  illustrated  by  photographs, 
have  been  mentioned.  There  are  many  more  of  such 
details  and  it  is  assumed  that  the  architect  and  builder 
are  more  familiar  with  them  than  is  any  one  else. 

“Efflorescence  can  become  very  noticeable  on  the  wall 
of  a  building  composed  of  brick  or  other  masonry  ma' 
terials  that  are  exceptionally  low  in  soluble  salt  content 
if  an  excessive  amount  of  water  enters  that  wall. 

“Any  efflorescence  appearing  on  the  wall  of  a  building 
that  is  suitably  designed,  constructed  and  kept  in  repair 
in  order  to  avoid  excessive  water  penetration,  will  be 
due  to  rare  and  abnormal  conditions.  It  will  in  time 
gradually  diminish  and  finally  disappear.  It  will  never 
recur  under  normal  conditions  even  though  the  soluble 
salt  content  of  the  entire  wall  be  higher  than  is  normally 
the  case.  Prolonged  and  heavy  wind-driven  rains  will 
bring  out  efflorescence  on  almost  any  wall,  but  this 
efflorescence  is  of  the  temporary  nature  described,  is 
usually  of  short  duration,  and  is  generally  unaccompanied 
by  disintegration  of  joints. 

“The  effort  on  the  part  of  manufacturers  of  face  brick 
to  develop  products  as  free  as  possible  from  soluble  salts 
(even  if  the  goal,  complete  elimination,  could  be  attained) 
will  not  in  itself  insure  against  the  development  of 
efflorescence  on  walls.  Their  work  must  be  supple¬ 
mented  by  a  concentrated  effort  on  the  part  of  archi¬ 
tects,  builders  and  owners  to  keep  the  walls  as  dry  as 
possible.  It  is  also  very  necessary  that  manufacturers  of 
the  other  building  materials  used  in  walls  with  the  face 
brick  be  equally  concerned  with  the  question  of  soluble 
salts  in  their  materials. 

“Means  of  preventing  efflorescence  by  keeping  the 
walls  dry  have  been  outlined.  It  is  hoped  that  architects 
and  builders  generally  will  proceed  much  further  with 
this  study  and  that  the  face  brick  industry  will  have 
their  full  co-operation  in  keeping  dry  the  face  brick  walls 
of  buildings  yet  to  be  constructed.” 


WET  WALLS  AND  EFFLORESCENCE 

(Publication  Approved  by  the  Director  of  the  Bureau  of  Standards  of  the  U.  S.  Department  of  Commerce) 

I.  Certain  Fundamental  Principles 


THE  fundamental  cause  of  efflorescence  on  the  exterior 
walls  of  buildings  has  been  found  to  be  generally  due 
to  soluble  salts  in  masonry  materials.  (x,  2,  3  and  4.) 

No  masonry  material  is  always  exempt  under  all  condi- 
tions  from  contributing  to  the  development  of  noticeable 
efflorescence  on  the  exterior  surface  of  the  wall  of  a  build' 
ing.  This  is  true  whether  such  material  be  used  either  in 
the  facing  or  among  the  backing  up  materials  of  the  wall. 

In  the  investigation2  conducted  by  the  American  Face 
Brick  Association  at  the  National  Bureau  of  Standards,  55 
types  of  face  brick  from  as  many  different  manufacturers 
in  various  parts  of  the  United  States  were  examined  for 
soluble  salts.  Incidentally,  during  this  investigation  six 
different  types  of  common  brick  were  similarly  examined. 

The  majority  of  the  face  brick  contained  less  than  0.05  per 
cent  of  soluble  sulfuric  anhydride,  an  amount  insufficient  to 
cause  efflorescence  under  conditions  favorable  for  such. 
The  soluble  salt  content  of  the  common  brick  exceeded 
somewhat  this  amount  in  all  six  cases,  the  average  being 
0.16  per  cent.  During  this  same  investigation,  four  each 
of  widely  used  limes,  portland  cements  and  bricklayers’ 
cements  were  studied  in  order  to  determine  their  tendencies 
to  develop  efflorescence.  It  was  found  that  these  materials 
used  as  mortars  in  panels  constructed  with  the  55  different 
types  of  face  brick  did  actually  contribute  to  efflorescence 
on  the  panels.  The  lowest  sulfuric  anhydride  content  of 
the  four  limes  used  was  0.5  per  cent.  This  was  mainly  in 
the  form  of  calcium  sulfate,  a  soluble  salt.  The  portland 
cements  studied  contained  varying  amounts  of  calcium 
sulfate  of  necessity  added  by  the  manufacturer  to  retard 
the  set  of  the  cement.  All  of  the  bricklayers’  cements  con' 
tained  appreciable  quantities  of  soluble  salts.  The  be' 
havior  of  these  mortar  materials  in  the  panel  tests  is  dis- 
cussed5  in  the  report  to  architects  and  users. 

J.  S.  Rogers4  investigated  35  commercial  chemical  limes 
which  are  generally  conceded  to  be  at  least  as  free  from 
soluble  sulfates  as  the  limes  used  for  building  purposes. 
He  found  these  limes  to  contain  from  a  trace  to  1.50  per 
cent  of  sulfuric  anhydride  and  suggests  that  this  was  intro' 
duced  by  burning  limestone  with  coal  containing  sulfur. 
It  is  reasonable  to  assume  that  a  considerable  portion  of 
this  sulfuric  anhydride  in  these  chemical  limes  was  in  the 
form  of  calcium  sulfate,  a  soluble  salt  very  often  present 
in  the  efflorescence  material. 

In  Bureau  of  Standards  Technologic  Paper  349,  pages 
540  et  seq.,  it  is  shown  that  the  sulfates  of  calcium  and 
magnesium  sometimes  contained  in  brick  and  mortar  ma¬ 


terials,  are  also  contained  in  various  limestones  used  in  the 
building  industry.  It  is  further  shown  in  this  publication 
(pages  528  et  seq.)  that  soluble  organic  material,  causing  a 
brown  discoloration,  is  often  present  in  such  limestones. 

Two  facts  must  be  well  understood.  First,  the  soluble 
salts  are  not  confined  to  any  one  building  material,  but  are 
widely  distributed  among  practically  all  of  such  materials 
and,  second,  the  condition,  wet  walls,  is  most  favorable 
for  the  development  of  efflorescence  produced  by  such  salts. 

Thus  the  wide  occurrence  of  these  soluble  salts  among 
various  building  materials  becomes  apparent.  It  is  essen¬ 
tial  that  this  fact  be  borne  in  mind  if  there  is  to  be  co¬ 
operation  on  the  part  of  all  manufacturers  and  producers 
of  masonry  materials  with  architects  and  builders.  They 
must  also  use  precaution  to  reduce  the  amount  of  moisture 
penetration  into  walls  containing  these  salts  and  thereby 
overcome  this  annoyance,  efflorescence. 

Wet  walls  also  accelerate  disintegration 

Aside  from  being  the  direct  cause  of  efflorescence,  an 
excessive  amount  of  moisture  in  the  materials  of  a  wall 
accelerates  disintegration  of  such  materials  through  alter¬ 
nate  freezing  and  thawing  of  this  moisture  in  the  wall. 
Damp  interiors  are  often  another  undesirable  condition 
attending  the  disintegration  and  occurrence  of  efflores¬ 
cence.  It  is  therefore  seen  that  a  study  of  efflorescence 
from  the  standpoint  of  proper  design,  construction  and 
maintenance  must  of  necessity  involve  also  certain  phases 
of  the  study  of  both  disintegration  of  materials  in  walls 
and  damp  interiors.  This  is  the  most  important  reason 
for  making  a  concentrated  effort  in  all  future  construction 
to  make  and  preserve  dry  walls. 

In  view  of  such  facts  the  manufacturers  of  face  brick 
are  at  present  outlining  a  future  study  of  a  great  many  of 
the  factors  involved  in  creating  and  maintaining  the  best 
possible  conditions  for  their  material  in  the  walls  where 
they  are  to  be  used.  Obviously,  since  face  brick  must  be 
used  with  many  other  materials  in  such  walls,  such  a  study 
involves  not  only  the  building  units,  brick,  but  also  assem¬ 
blages  of  units  of  brick  together  with  units  of  various 
other  materials. 

In  the  investigation  of  causes  of  and  remedies  for  efflores' 
cence  on  face  brick  walls5,  it  developed  that  the  soluble 
salts  that  would  otherwise  be  present  in  clay  products 
used  in  construction  can  be  practically  eliminated  by  the 
manufacturer  of  such  materials  by  certain  procedures  in 
the  drying  and  burning  of  his  ware,  together  with  the 


■Efflorescence  and  Capillary  Fissures  in  Cement  Mortars,  “Rock  Products",  Vol.  30,  Feb.  5,  1927,  Page  83. 

2Cause  and  Prevention  of  Kiln  and  Dry  House  Scum  and  of  Efflorescence  on  Face  Brick  Walls,  L.  A.  Palmer,  Bureau  cf  Standards  Technologic  Paper  No.  370. 

3The  Physical  Properties  of  the  Principal  Commercial  Limestones  Used  for  Building  Construction  in  the  United  States,  D.  W.  Kessler  and  W.  H.  Sligh,  Bureau  of  Stan¬ 
dards  Technologic  Paper  No.  349,  pages  540  et  seq.  Also  pages  526  et  seq. 

*Oom  posit  ion  of  Commercial  Chemical  Limes,  J.  S.  Rogers,  “Industrial  and  Engineering  Chemistry,"  Vol.  19,  Oct.  1927.  Page  115/. 

Efflorescence  on  Face  Brick  Walls,  L.  A.  Palmer,  Special  Report  to  Architects  and  Users  of  Face  Brick.  (See  page  24  of  this  book.) 


WET  WALLS  AND  EFFLORESCENCE 


9 


judicious  use  of  barium  compounds  in  his  clay.  These  pro¬ 
cedures  are  at  present  being  generally  used  by  the  face 
brick  industry  and  in  part  justify  the  difference  in  cost 
between  face  brick  and  the  cheaper  clay  products,  hollow 
tile  and  common  brick  used  generally  as  backing  up  ma¬ 
terials.  From  an  economic  standpoint,  it  is  not  always 
practicable  for  the  manufacturers  of  common  brick  and 
hollow  tile  to  adopt  the  procedures  used  by  the  face  brick 
industry  in  eliminating  soluble  salts.  From  the  standpoint 
of  efflorescence  it  is  therefore  very  essential  that  these 
backing  up  materials  be  protected  from  excessive  water 
penetration.  These  efforts  on  the  part  of  face  brick  manu¬ 
facturers  to  reduce  the  amount  of  salts  in  their  own 
product  will  not  alone  suffice  in  eliminating  efflorescence. 

M ortar  made  water-repellent  by  stearates 

It  was  further  developed  during  the  above  mentioned 
investigation  (2  and  5)  that  the  addition  of  an  amount  of 
either  calcium  or  ammonium  stearate  with  mortar  ma¬ 
terials  reduced  the  extent  to  which  they  contributed  to 
efflorescence.  These  two  stearates  render  the  mortar 
more  water-repellent  and  an  amount  of  either  stearate 
equal  to  two  per  cent  by  weight  of  the  cement  or  of  the 
lime  or  of  the  lime  plus  the  cement,  if  both  cement  and 
lime  are  used,  is  suggested.  This  treatment  will  practi¬ 
cally  prevent  water  penetration  of  the  mortar  due  to 
capillary  forces  only. 

It  must,  however,  be  borne  in  mind  that  the  original 
moisture  introduced  during  construction  and  contained  in 
mortar  so  treated  may  be  subjected  to  freezing  to  an  extent 
sufficient  to  cause  cracking  of  the  mortar  joints.  Cracking 
of  mortar  joints  containing  the  water-repellent  materials 
may  also  occur  as  a  result  of  settlement,  ffence  it  is  seen 
that  no  chemical  treatment  of  materials  will  alone  suffice. 
Prompt  pointing  up  is  required  in  this  case  if  the  mortar 
so  treated  is  to  maintain  its  original  water-repellent 
property. 

Water  brings  salts  from  wall  interior 

Water  which  has  penetrated  to  the  interior  of  a  wall 
subsequently  usually  finds  its  way  through  the  pores  of 
the  masonry  to  the  face  brick  and  there  evaporates,  de¬ 
positing  any  salts  which  it  has  taken  into  solution  from 
the  backing  up  materials.  It  may  not  occur  to  one  who 
has  not  studied  the  subject  that  any  material  other  than 
that  which  he  sees  has  contributed  to  the  unsightly  ap¬ 
pearance  of  the  wall.  The  salts  thus  being  left  on  the 
face  brick  may  lead  one  to  conclude  that  the  face  brick 
are  directly  responsible,  whereas  they  may  have  been 
practically  free  from  soluble  salts  originally. 

Summing  up,  it  is  seen  that  whereas  the  fundamental 
cause  of  efflorescence  is  the  presence  of  soluble  salts  in 
the  materials  of  the  wall,  the  immediate  cause  is  excessive 
moisture  penetration  into  the  wall.  To  avoid  the  latter 
condition  requires  the  full  cooperation  of  architects  and 
builders  as  well  as  manufacturers  of  all  masonry  materials. 


Analysis  of  wall  conditions 

For  convenience,  the  conditions  obtaining  generally  in 
the  occurrences  of  efflorescence  may  be  classified  as  follows : 

Excessive  water,  normal  salts 

A.  The  condition:  more  than  the  normal  or  usual 
amount  of  water  penetration  of  a  wall  containing  a  normal 
or  average  amount  of  soluble  salts,  the  excessive  water 
penetration  being  due  to  either  faulty  design,  construction 
or  maintenance  or  to  combinations  of  these  undesirable 
conditions. 

Excessive  water,  excessive  salts 

B.  The  condition:  more  than  the  normal  or  usual  ex¬ 
tent  of  water  penetration  of  a  wall  containing  more  than 
the  usual  amount  of  soluble  salts,  the  high  degree  of  water 
penetration  being  due  to  the  same  causes  given  under  A. 

? formal  water,  normal  salts 

C.  The  development  of  efflorescence  attended  by  the 
condition:  normal  amount  of  water  penetration  of  a  wall 
containing  a  normal  or  average  quantity  of  soluble  salts. 

formal  water,  excessive  salts 

D.  The  appearance  of  efflorescence  with  the  condition: 
normal  water  penetration  of  a  wall  containing  a  relatively 
large  amount  of  soluble  salts. 

In  the  above  classifications,  “normal  water  penetration” 
and  “normal  or  average  amount  of  soluble  salts”  are  only 
relative  and  arbitrary  terms.  No  one  has  defined  either 
condition.  However,  it  is  reasonable  to  hypothesize  the 
existence  of  such  conditions.  Most  careful  observers  and 
practically  all  architects  and  builders  will  recognize  an  ex¬ 
treme  condition  as  regards  water  penetration.  Most 
chemists  familiar  with  building  materials  will  recognize  an 
extreme  condition  if  the  average  salt  content  of  the  ma¬ 
terials  in  the  wall  is  greater  than  two  per  cent  by  weight 
of  total  mass  of  materials  and  another  and  highly  favorable 
extreme  condition  if  the  salt  content  is  below  0.01  per 
cent  of  the  total  weight  of  masonry.  Either  condition 
will  seldom  be  realized. 

Cases  involving  excessive  moisture  most  frequent 
and  most  serious 

Normal  or  average  water  penetration  is  exceeded  by 
every  instance  of  a  leaking  downspout,  dripless  sills,  de¬ 
fective  flashing  of  parapet  walls,  etc.  If  one  were  to 
estimate  as  to  which  of  conditions,  A,  B,  C  and  D  pre¬ 
dominate  in  the  numerous  instances  of  efflorescence,  he 
would,  following  an  extended  field  study,  most  likely  con¬ 
clude  that  conditions  A  and  B  obtain  in  by  far  the  majority 
of  cases.  There  are  certain  other  things  also  that  would 
become  evident  after  such  a  study.  It  would  be  noted 
that  conditions  A  and  B  are  the  ones  most  usually  at¬ 
tended  by  disintegration  of  the  wall.  It  is  evident  that 
in  all  cases  of  excessive  water  penetration,  alternate  freez¬ 
ing  and  thawing  are  especially  severe  and  disrupt  the 
masonry  in  time. 


10 


WET  WALLS  AND  EFFLORESCENCE 


Furthermore,  after  long  and  constant  observation  of 
buildings  which  develop  efflorescence  under  the  condi- 
tions,  C  and  D,  the  observer  will  note  that  such  occur¬ 
rences  are  usually  temporary.  The  efflorescence  will  in 
such  cases  gradually  diminish  more  and  more  and  finally 
never  again  appear.  In  these  instances  also  one 
seldom  notes  any  wall  disintegration.  This  would  indi¬ 
cate  that  wall  disintegration  is  not  a  consequence  of 
efflorescence  but  rather  that  it  is  an  attendant  cir¬ 
cumstance,  the  two,  efflorescence 
and  disintegration  usually  occurring 
simultaneously  under  the  conditions 
A  and  B  and  from  the  same  im¬ 
mediate  cause,  i.e.,  excessive  water 
penetration  of  the  wall. 

If  brick  are  used  which  have  had 
no  barium  treatment  or  if  the  drying 
and  burning  conditions  were  not  so 
controlled  as  to  insure  their  having  a 
low  soluble  salt  content,  there  will 
result  then  either  condition,  B,  the 
worst  of  the  four  conditions,  or  con¬ 
dition  D,  which  though  better  than 
B  is  yet  very  undesirable. 

Condition  A  is  second  in  undesir¬ 
ability  only  to  B.  It  is  chiefly  within 
the  power  of  architects  and  builders 
to  eliminate  condition  A.  To  relieve 
condition  B  requires  effort  on  the 
part  of  producers  of  masonry  ma¬ 
terials  as  well  as  architects  and 
builders.  The  producers  alone  are 
responsible  for  condition  D. 

Condition  C  is  the  best  of  the 
four.  Efflorescence  appearing  under 
this  condition  is  at  the  worst  only  temporary  and 
usually  it  is  little  more  than  barely  noticeable. 

Melting  snow  may  saturate  walls 

It  often  happens  that  certain  structural  or  maintenance 
defects  on  buildings  are  so  located  that  saturation  of  the 
walls  at  such  places  can  only  occur  through  the  melting 
of  snow.  On  account  of  large  overhangs,  such  locations 
are  amply  protected  from  moisture  in  the  form  of  rain. 
Nevertheless,  driven  snow  can  readily  accumulate  at  these 
places.  When  melting,  this  snow  will  saturate  the  walls 
beneath  the  overhangs  and  produce  efflorescence  and  dis¬ 
integration  in  such  locations  during  early  spring.  This 
is  one  of  many  reasons  for  the  great  prevalence  of  efflores¬ 
cence  during  the  early  spring  season. 


It  can  be  noted  in  almost  any  city  that  along  with  the 
usual  white  efflorescence,  on  the  same  building  there  may 
be  seen  unsightly  stains  on  the  faces  of  belts  and  cornices. 
In  most  cases,  failure  to  provide  drips  at  the  nibs  of  the 
projecting  cornices  is  the  direct  cause  of  the  streaks  and 
stains  on  the  stone,  terra  cotta,  etc.  Solid  particles  of 
soot  settle  on  the  washes,  become  softened  by  rain  and 
run  down  the  face  of  the  moldings.  These  discolorations 
are  cumulative  and  in  most  manufacturing  cities  become 

jet  black.  The  soot  contains  more  or 
less  of  sulfur  which  gives  to  water  in 
contact  with  it  acidic  properties 
which  may  be  a  factor  in  disintegra¬ 
tion  of  mortar  joints,  making  soluble 
otherwise  insoluble  material. 

Drips  greatly  reduce 
water  penetration 

While  it  is  true  that  drips  at  the 
nibs  may  in  some  cases  slightly  modify 
the  customary  proportions  of  certain 
members,  the  advantage  gained  in  re¬ 
ducing  water  penetration  is  sufficient 
to  outweigh  any  such  objection. 
Quoting  from  Bureau  of  Standards 
Technologic  Paper  No.  132:  “Where 
rain  falls  on  the  top  surface  of  a  pro¬ 
jection,  it  runs  over  the  outer  edge 
and  following  the  lower  surface 
reaches  the  wall  which  becomes  soak¬ 
ed  for  some  distance  below.  Also 
snow  which  is  allowed  to  remain  on 
these  projections  finally  melts  and 
causes  the  same  difficulty.  By  the 
simple  method  of  ‘throating’ — that 
is,  making  a  groove  in  the  lower  sur¬ 
face  of  projecting  members  — this  difficulty  is  overcome, 
as  the  water  when  it  reaches  this  groove  drops  to  the 
ground.”  Further  than  this,  only  a  little  consideration 
is  necessary  to  clearly  see  that  a  small  drip  groove  is 
of  little  value,  as  the  droplets  of  water  can  span  such.  It 
is  good  practice  to  make  the  grooves  at  least  fP  wide  and 
deep.  Another  necessary  precaution  is  to  have  the 
projection  at  the  rear  of  a  coping  at  least  2"  to  give  room  for 
a  drip  of  this  size  and  to  keep  the  drip  away  from  the  wall. 
FIGURE  1  illustrates  the  conventional  profile.  FIGURE  2 
is  no  less  pleasing  to  the  eye  as  regards  profile  and  will 
serve  to  keep  the  moldings  clean,  whereas  water  and  dirt 
will  run  down  the  face  of  the  moldings  of  FIGURE  1  and 
disfigure  it  as  well  as  the  face  brick  or  other  materials  be¬ 
low  it  in  the  wall. 


Dirt  from  wash 
wifi  run  c/owr?  { 
face  of  mould-  // 
inqs 

Figure  1 .  Conventional  profile 


Drip  of-  nib  ^ 
wifi  keep 
the  mouldings 
clean 


Figure  2.  Improved  profile 


II.  Field  Work 


SUPPLEMENTARY  to  the  work  of  finding  necessary- 
fundamental  facts  concerning  the  development  of  efflor' 
escence,  William  C.  Koch  of  the  Research  Committee 
of  the  American  Face  Brick  Association,  undertook  an 
extensive  study  for  the  purpose  of  correlating  these  facts 
with  the  subjects  of  design,  construction  and  maintenance. 
Certain  buildings  which  were  prone  to  develop  efflorescence 
were  observed  carefully  from  season  to  season  and  some  facts 
not  at  all  obvious  at  first  were  brought  out.  Finally  an 
intensive  field  study  was  made  in  which  250  cases  of 
efflorescence  and  the  usual  accompaniment,  wall  disim 
tegration,  were  studied  and  an  attempt  was  made  to 
interpret  these  data.  With  but  one  or  two  definite  excep' 
tions,  the  250  instances  of  discoloration  and  disintegration 
could  have  been  prevented  by  either  proper  design,  com 
struction  or  maintenance.  In  some  cases  only  one  of 
these  three  factors  was  the  direct  cause,  but  usually  there 
were  two  and  in  a  number  of  cases  all  three  were  at  fault. 

Efflorescence  was  observed  on  almost  every  type  of 
building  material.  The  efflorescence  on  stone  which  is  more 
nearly  the  color  of  the  stone  was  often  not  apparent  until 
a  close  examination  was  made.  This  same  efflorescence 
would  have  been  very  conspicuous  had  the  stone  been  as 
dark  in  color  as  brick. 

Prompt  pointing  up  of  mortar  joints  essential 
In  some  instances  the  joints  in  the  wall  areas  were  care' 
fully  pointed  up  following  the  first  few  occurrences  of 
efflorescence.  Due  to  settlement,  cracks  often  appeared 
and  this  condition  augmented  the  penetration  of  water 
into  the  interior  of  the  wall.  Where  prompt  pointing 
up  was  not  done  and  where  the  condition  had  lasted  over 
a  period  of  years,  disintegration  of  the  mortar  joints  almost 
invariably  had  occurred.  In  any  case  where  underburned 
brick  had  been  used,  these  also  had  become  disintegrated. 

In  the  atmosphere  of  cities  consuming  annually  large 
quantities  of  bituminous  coal,  the  sulfur  dioxide  so  lib' 
erated  in  conjunction  with  water  in  the  form  of  rain  or 
melting  snow  may  accelerate  the  disintegration  of  certain 
masonry  materials.  Parr6  in  discussing  the  prevalence 
of  sulfur  dioxide  in  the  atmosphere  makes  the  following 
statement: 

“I  recall  a  certain  dwelling  far  removed  from  possible 
contamination  by  gases  from  coal  fires  where  the  window 
screens  have  remained  continually  in  place  for  twenty 
years.  The  iron  wire  of  which  they  are  made  is  still  whole 
and  sound,  whereas  the  iron  wire  screens  of  another 
dwelling  in  the  center  of  the  soft  coal  belt  corroded  and 
fell  completely  out  of  their  frames  after  one  winter  season.” 

Professor  Parr  states  further  that  the  annual  combustion 
of  600  millions  of  tons  of  coal,  mostly  bituminous,  in  the 
United  States  liberates  approximately  40  billion  pounds 
or  400  billion  cubic  feet  of  sulfur  dioxide,  most  of  which  is 


concentrated  in  manufacturing  centers.  If  sulfur  dioxide 
from  this  source  is  in  concentration  sufficient  to  corrode 
an  iron  wire  screen  in  one  season,  it  very  likely  also  would 
tend  to  corrode  any  masonry  material  containing  lime, 
such  as  mortar  or  limestone.  (3  and  7)  All  brick  manu' 
facturers  know  what  sulfur  dioxide  will  do  to  a  clay 
containing  limestone  in  a  humid  drying  chamber. 

Face  bric\  resistent  to  acid  solutions 

On  the  other  hand,  the  author  has  made  numerous  tests 
with  concentrated  solutions  of  sulfur  dioxide  in  water  on 
face  brick.  In  all  cases  the  solvent  action  of  this  reagent 
was  negligible.  In  by  far  the  majority  of  cases  there  was 
no  solvent  action  whatsoever.  In  addition,  the  author 
immersed  face  brick  in  fairly  concentrated  acid  solutions, 
such  as  ten  per  cent  solutions  of  hydrochloric,  nitric  and 
sulfuric  acids  for  periods  of  from  ten  days  to  two  weeks. 
While  these  acids  are  sufficiently  strong  to  rapidly  dis' 
solve  certain  limestones,  the  brick  thus  treated  remained 
practically  unchanged.  It  is  reasonably  safe  to  assume 
that  underburned  brick  would  not  have  been  so  resistent 
generally. 

In  the  light  of  the  above  comments  by  Professor  Parr, 
it  is  very  likely  that  sulfur  dioxide  of  the  atmosphere  can 
accelerate  any  decomposition  of  mortar  joints  initially 
begun  by  frost  action  or  cracking  due  to  settlement. 
Prompt  pointing  up  of  joints  is,  therefore,  very  necessary 
and  further  than  this  since  pointing  up  is  usually  required 
on  those  portions  of  the  wall  most  exposed  to  excessive 
moisture  penetration,  mortar  containing  the  water-repeb 
lent  stearates  should  be  considered  for  such  pointing  up. 

Snow  water  may  hasten  mortar  disintegration 

In  connection  with  the  field  work,  some  analyses  of 
snow  water  were  made.  In  one  instance  water  from 
melted  snow  accumulating  over  a  period  of  three  months 
in  a  small,  open  area  in  the  city  of  St.  Paul  contained 
0.005  per  cent  of  sulfuric  anhydride.  This  water  was 
distinctly  acid,  the  “pH”  (logarithm  of  the  reciprocal  of 
the  hydrogen  ion  concentration)  being  3.5.  Water  of 
this  acidity  could  easily  attack  the  lime  of  mortar  or 
certain  limestones  (forming  soluble  calcium  sulfate)  if 
left  in  contact  with  such  building  materials  for  consider' 
able  periods  of  time.  Such  water  entering  cracks  due 
to  settlement  or  frost  action  would  tend  to  accelerate 
any  disintegration  of  mortar.  Here  then  is  another 
possible  source  of  efflorescence. 

Careful  and  prompt  pointing  up  of  mortar  joints  is 
especially  necessary  in  brick  masonry  as  a  safeguard 
against  efflorescence,  as  observations  showed.  For  ex' 
ample,  consider  two  walls,  one  of  stone  and  one  of  brick. 
The  ratio  of  amount  and  number  of  exits  (principally 
joints)  in  brick  work  to  those  in  stone  work  is  such  as  to 


6Some  Combustion  Problems  in  their  Relation  to  Public  Health,  Samuel  W.  Parr,  “Industrial  and  Engineering  Chemistry,”  Vol.  20,  May  5,  1928,  Page  454 

7H.  Pemberton,  Journal  Franklin  Inst.  Vol.  106,  Page  62 


12 


WET  WALLS  AND  EFFLORESCENCE 


promote  freer  flow  of  water  in  the  wall  of  brick,  carrying  good,  cracking  became  noticeable  at  the  left  end  of  the  stone 
the  salts  to  the  surface.  Furthermore,  joints  in  stone  coping  due  to  settlement.  Water  leaks  through  this  crack  and 
are  generally  thinner  than  those  in  brickwork  and  the  through  similar  ones  not  visible  and  particularly  through 
area  of  each  joint  in  the  latter  case  is  consequently  greater  the  crack  along  the  entire  length  of  stone  and  back  of  same 
than  in  the  case  of  stonework.  These  dimensional  fac-  whence  it  easily  penetrates  to  the  face  of  the  brick  wall  at 
tors  result  in  restricted  flow  of  saltdaden  water  in  the  the  points  where  vertical  joints  in  the  stone  and  between 


case  of  stone.  This  fact  may  account 
in  part  for  the  popular  notion  that 
limestone  and  sandstone  contain  very 
little  of  soluble  material. 

FIGURE  3  shows  efflorescence  on  red 
sandstone.  Water  penetrated  the  wall, 
draining  in  from  the  small  porch  over 
this  discoloration.  In  FIGURE  4  there 
is  seen  efflorescence  on  both  the  brick' 
work  and  stone  arches  beneath  the  win' 
dow  jutting  through  the  lower  part 
of  the  roof.  The  design  in  this 
case  is  very  favorable  for  carrying 
water  into  the  wall  at  the  area 
covered  by  the  white  salts.  FIGURE  5 
shows  again  efflorescence  on  sandstone. 
Prompt  pointing  up  of  the  cracks  be' 
tween  mortar  joints  and  stone  due  to 
settlement  would  have  prevented  this. 
FIGURE  6  shows  efflorescence  on 
porch  cheeks  of  concrete  block  due  to 
seepage  and  splashing  at  the  base  and 
in  addition  to  this,  water  has  entered 
from  the  porch  floor.  Moisture  also 
has  progressed  down  the  column  from 
the  cap  of  the  porch  pier. 

Settlement  crac\s  need  immediate 
attention 

It  is  reasonable  to  assume  that  crack' 
ing  of  joints  due  to  settlement  is  more 
likely  to  occur  at  the  bond  of  stone 
copings,  sills,  etc.,  than  it  is  among  the 
joints  between  the  brick  in  a  wall  faced 
with  brick.  This  assumption  is  more 
justifiable  when  stone  or  brick  walls 
exposed  to  a  normal  amount 
of  water  penetration  are 
being  considered.  Evidence 
for  this  assumption  was 
found  in  many  instances  and 
FIGURE  7  is  an  lllustra' 
tion  of  one.  The  brick 
being  small  units,  the 
stresses  induced  by  settle' 
ment  tend  consequently  to 
be  more  evenly  distributed 
than  in  the  case  of  a  wall 
built  entirely  of  stone.  In 
FIGURE  7  although  the 
construction  was  originally 


Figure  3.  Efflorescence  on  red  sandstone, 
below  porch. 


Figure  4. 


Efflorescence  on  both  brickwork 
and  stone  arches. 


the  stone  and  the  brick  have  disintegra' 
ted  or  have  cracked  open.  A  little  point' 
ing  up  should  have  been  done  promptly. 

In  this  connection  it  is  well  to  con' 
sider  that  the  number  of  mortar  joints 
per  unit  area  of  a  brick  wall,  being  con' 
siderably  greater  than  the  number  of 
such  in  the  same  area  of  a  wall  built 
entirely  of  stone  as  above  mentioned, 
water  can  therefore  flow  more  freely 
into  the  wall  built  of  brick  on  account 
of  this  larger  area  of  mortar.  Referring  to 
FIGURE  7,  there  is  then  consequently 
more  water  penetration  in  the  brick  wall 
below  the  stone  coping  which  has 
cracked  loose  from  the  mortar  bond  due 
to  settlement  than  would  have  obtained 
were  the  wall  built  entirely  of  stone. 
It  is  not  therefore  that  in  the  matter  of 
proper  maintenance  more  pointing  up 
is  required  in  a  wall  built  of  brick,  but 
it  is  the  fact  that  prompt  pointing  up 
is  of  especial  importance.  It  is  also 
apparent  that  there  being  more  mortar 
material  in  the  brick  wall,  any  contribu' 
tion  which  a  given  mortar  makes  to  the 
development  of  efflorescence  is  greater 
in  a  brick  than  in  a  stone  wall. 

More  consideration  should  be  given 
to  the  future  use  of  a  building  by  those 
who  design  and  construct  it.  FIGURE  8 
shows  a  creamery  covered  in  places 
by  efflorescence.  A  photograph  of  this 
structure  taken  two  years  previous  to 
the  time  of  obtaining  the  one  here  given 


Figure  6.  Efflorescence  on 
concrete  block. 


Figure  5.  Prompt  pointing  up  of  cracks  in  the  mortar  joints  would 
have  prevented  this  efflorescence  (on  sandstone'. 


WET  WALLS 


AND  EFFLORESCENCE 


13 


Figure  7.  The  stone  coping  has  broken  loose  from  the  adjoining 
masonry,  allowing  water  to  enter  the  brickwork. 


Figure  10.  Leaking  downspouts  are  frequent  sources  of  water 
penetration,  leading  to  efflorescence. 


Figure  8.  Water  condenses  on  the  inner  walls  of  this  creamery  except 
in  the  office,  which  is  at  the  right. 


Figure  9.  Closer  view  of  wall  shown  above.  Note  disintegration  of 

mortar  joints. 


also  shows  efflorescence  appearing  on 
the  same  parts  of  the  wall  as  those 
covered  with  such  in  this  case,  two 
years  later.  Water  condenses  inside 
where  operations  are  carried  on.  The 
middle  portion  of  the  exterior  wall 
to  the  right  is  free  from  efflorescence. 
This  area  is  the  outer  wall  of  the 
company’s  office  and  consequently 
there  was  a  dryer  interior  at 
this  locality.  The  efflorescence 
in  this  instance  could  possibly  have 
been  prevented  altogether  or 
at  least  considerably  reduced  by 
waterproofing  the  entire  inner  walls 
of  the  humid  rooms.  Waterproofing 
the  exterior  surface  of  these  walls 
would  merely  result  in  a  progressive 
accumulation  of  the  efflorescence  at 
those  areas  where  the  exterior  coat' 
ing  of  waterproofing  material  is  de- 
fective.  Such  areas  are  always  de- 
veloped  to  a  greater  or  lesser  extent. 

Among  the  various  types  of 
faulty  maintenance,  leaking  rain 


Figure  11.  Efflorescence  closely  follows  the 
downspout  on  this  limestone  wall,  showing 
penetration  of  moisture. 


leaders  and  gutters  are  very  numer¬ 
ous.  FIGURES  9  and  10,  photo¬ 
graphs  of  the  same  wall,  amply  illus¬ 
trate  the  disintegration  induced  first 
by  cracks  due  to  settlement  and 
later  accelerated  by  the  excessive 
penetration  of  water  due  to  a  leak¬ 
ing  downspout.  In  this  instance, 
the  mortar  joints  have  disintegrated. 
The  courses  of  brick  projecting  out¬ 
ward  from  the  wall  add  to  the  ex¬ 
cessive  accumulation  of  moisture. 
This  point  relative  to  design  will 
be  further  illustrated  in  this  report. 
Again,  note  the  efflorescence  near 
the  downspout  in  FIGURE  1 1. 
This  wall  is  of  limestone  and  its 
color  is  nearly  the  same  as  that  of 
the  salts  of  efflorescence . 

Gutter  drains  should  be  higher 
toward  the  building.  A  few  in¬ 
stances  were  noted  where  the  re¬ 
verse  was  the  case  and  in  many  in¬ 
stances,  the  level  toward  the  wall 
was  the  same  as  that  farthest  from 


14 


WET  WALLS  AND 


EFFLORESCENCE 


Figure  12.  Excessive  moisture  has  here  caused  the  disintegration  of 
paint,  as  in  numberless  instances. 


Figure  13a.  Seepage  and  splashing  have  brought  about  extensive 
stucco  disintegration  at  the  base  of  this  building. 


Figure  13b.  In  addition  to  causing  efflorescence,  excessive  water 
penetration  has  here  resulted  in  disintegration  of  the  stucco,  which 
has  fallen  off,  exposing  the  brickwork  beneath. 


Figure  14a.  The  unusually  severe  exposure  of  this  wall  has  resulted 
in  marked  efflorescence. 


Figure  14b.  In  this  view  of  the  same  wall,  note  the  peeling  of  paint 
and  the  failure  of  mortar  joints. 


Figure  14c.  Here  is  the  final  collapse  of  part  of  the  wall  shown  in 
the  above  illustrations. 


Figure  14d.  In  this  addition  to  the  same  wall,  both  the  stucco  cover 
and  the  mortar  joints  are  disintegrating. 


WET  WALLS  AND  EFFLORESCENCE 


15 


the  wall.  It  is  also  necessary  that  gutters  and  drains  be  and  construction,  it  is  seen  that  in  the  newer  part,  14d, 
of  ample  capacity  for  carrying  away  water  from  heavy  the  brick  are  not  covered  by  earth.  There  is  a  concrete 
rains.  Also,  at  the  returns  of  porch  roofs  where  overflow  base  in  this  case.  However,  the  design  of  the  sills  is 
will  result  in  discoloration  and  cracking  of  masonry  wrong,  they  having  no  drips,  and  there  are  no  eaves; 
material,  special  attention  should  be  given  to  the  design  of  hence,  covering  the  brick  with  stucco  brought  no  material 
gutters  and  downspouts.  The  end  joints  should  be  benefit.  It  is  seen  that  the  stucco  cover  is  beginning  to 
thoroughly  protected  with  sheet  lead,  copper  or  other  disintegrate,  showing  the  brick  underneath.  The  mortar 


suitable  flashings. 

In  order  to  illustrate  the 
damaging  effect  generally  of 
exposure  of  all  building  ma' 
terials  to  an  excessive  amount 
of  moisture,  the  accompany' 
ing  photograph ,  FIGURE  1 2 , 
is  shown  as  a  typical  example 
of  numerous  instances  ob' 
served  of  paint  disintegration 
from  this  cause.  FIGURE 
13a  shows  disintegration  of 
stucco  at  the  base  of  a  build' 
ing  brought  about  by  seepage 
and  splashing.  The  eaves  are 
wide  enough  to  protect  most 
of  the  walls,  but  there  is  no  protection 
at  the  base.  The  stucco  was  at  the 
soil  level  originally.  FIGURE  13b  is 
another  example  of  disintegration  of 
stucco  resulting  from  excessive  water 
penetration. 

FIGURES  14a,  14b  and  14c  show  in 
increasing  order  of  magnitude  the  effect 
of  needless  exposure  of  a  wall.  Efflo' 
rescence  is  shown  in  (a),  in  (b)  is  seen 
efflorescence  and  disintegration  of  the 
mortar  joints,  and  (c)  shows  the  final 
collapse  of  the  wall.  FIGURE  14d 
shows  an  addition  to  the  building  made 
after  that  part  illustrated  by  FIGURES 
14a,  14b  and  14c  had  shown  signs 
of  deterioration.  By  profiting  partially 
by  past  mistakes  in  the  way  of  design 


Figure  15.  Maintenance  alone  is  at  fault  in  this  instanc 
the  gutters  are  defective. 


Figure  16.  The  downspout  leaks,  and  set¬ 
tlement  cracks  above  the  stone  set  in  the 
brickwork  have  not  been  pointed  up,  re¬ 
sulting  in  much  efflorescence. 


joints  are  also  beginning  to 
rapidly  disintegrate.  Note 
also  the  disintegration  of 
paint  in  the  illustrations, 
14a  and  14b.  This  is  also 
likely  due  to  the  unusually 
severe  exposure  of  the  wall. 

FIGURE  15,  unlike  the 
cases  14a,  14b,  14c  and 
14d,  is  a  case  of  faulty  main' 
tenance  only.  Due  to  defec' 
tive  gutters,  there  has  been 
more  than  normal  penetration 
of  water  into  the  wall.  If 
the  bales  are  fixed,  the  next 
good  rain  will  have  washed 
off  the  efflorescence  and  it  may  not 
recur.  FIGURE  16  is  another  example 
of  improper  maintenance.  The  design 
and  construction  were  all  right  in  this 
case.  The  downspout  is  leaking  and, 
what  is  worse,  there  has  been  no 
pointing  up  of  cracks  (due  to  settle- 
ment)  at  the  top  stone  courses. 

Excessive  water  penetration 
from  lac\  of  drips 

A  typical  example  of  wrong  design 
is  shown  in  FIGURE  17,  a  and  b. 
Both  are  pictures  of  the  same  build- 
ing.  There  are  no  drips  on  the  flat 
inclined  stone  caps  at  the  top  of  the 
buttress  piers  and  the  inevitable  result 
is  in  evidence. 


Figure  17a.  Efflorescence  caused  by  failure  to  provide  drips  on  the 
stone  caps  over  the  buttress  piers. 


Figure  17b.  Another  view  of  the  same  building  illustrating  the 
necessity  for  adequate  drips. 


16 


WET  WALLS  AND  EFFLORESCENCE 


Figure.  18.  This  general  efflorescence,  chiefly  on  the  mortar 
joints,  probably  came  from  excessive  salts  in  the  wall. 


Figure  19.  Water  has  penetrated  these  walls  of  underburned  brick, 
because  of  poor  design  and  poorly  constructed  coping. 


Figure  20.  Flashing  should  be  carried  completely  through  the 
parapet  wall  to  keep  water  from  penetrating  downward. 


Figure  21.  Efflorescence  has  appeared  in  this  case  below  the 
water  exit  in  the  parapet  wall. 


Figure  22a.  Defective  flashing,  absence  of  suitable  drips  and  Figure  22b.  Faulty  maintenance  is  also  responsible  in  part  for 

projections  at  the  buttress  tops  caused  this  trouble.  the  efflorescence  shown  on  this  church. 


WET  WALLS  AND  EFFLORESCENCE 


17 


It  is  very  probable  that  condition  D,  namely  normal 
water  penetration  of  a  wall  containing  more  than  the  usual 
amount  of  salts,  obtained  in  the  case  of  the  building, 
FIGURE  18.  The  efflorescence  was  in  this  case  generally 
distributed  over  the  wall.  This  building  is  new  and  the 
design  and  construction  were  good.  It  may  be  noted  that 
the  efflorescence  was  in  this  instance  mainly  on  the  mortar 
joints.  It  is  likely  that  these  salts  were  carried  outward 
to  the  surface  by  evaporation  of  the  moisture  absorbed 
and  entrapped  during  construction. 

Bric\  walls  need  protection  during  construction 
Mention  should  be  made  here  of  the  need  of  protection 
of  brick  walls  during  the  process  of  construction  from 
avoidable  exposure  to  moisture.  The  tops  of  unfinished 
walls  should  be  well  covered  with  canvas  or  tar  paper  at 
the  end  of  each  day’s  work. 

Proper  flashing  essential 
Defective  flashing  is  one 
of  the  most  numerous  of 
the  immediate  causes  of 
efflorescence  and  wall  dis¬ 
integration  and  often  also 
there  are  in  addition  poorly 
designed  and  constructed 
copings.  Wall  copings, 

cornices,  rails,  chimney 
caps,  etc.,  should  be  built 
of  concrete,  stone,  terra 
cotta  or  metal  with  ample 
overhanging  drip  groove  or 
lip,  and  watertight  joints. 

FIGURE  1 9  shows  a  building  constructed  of  underburned 
brick,  which  have  been  subjected  to  freezing  and  thawing 
of  water  penetrating  into  the  interior  of  the  wall  through 
poor  design  and  poorly  constructed  coping.  This  building 
is  old  and  it  is  likely  that  the  underburned  brick  that  have 
in  this  case  disintegrated  to  some  extent,  were  burned 
in  scove  kilns  which  in  early  days  were  fired  with 
wood.  FIGURE  20  is  a  typical  example  of  defective 
flashing  on  a  parapet  wall.  Note  the  efflorescence  below 
the  water  exit  in  the  parapet  wall  illustrated  in  FIGURE  21. 
Considering  the  favorable  conditions  for  excessive  water 
penetration,  there  is  remarkably  little  efflorescence  on 
the  exterior  walls  of  the  church,  FIGURES  22a  and  22b. 
Defective  flashing,  together  with  the  absence  of  suitable 
drips  and  projections  at  the  stone  caps  at  the  tops  of 
the  buttress  piers,  is  directly  accountable  for  the  white 
efflorescence.  Faulty  maintenance  has  added  to  the  deplor¬ 
able  condition. 

In  the  case  of  parapet  walls  as  illustrated  by  FIGURE  20, 
the  flashing  should  be  carried  completely  through  the 
wall,  one  or  two  courses  above  the  roof  level.  The 
parapet  wall  is  then  completely  separated  by  an  impervious 
membrane  from  the  other  portion  of  the  wall  and  conse¬ 
quently  water  can  not  penetrate  downward  into  the  wall. 
Architects  should  also  waterproof  the  entire  inner  side  of 


the  wall  and  should  use  impervious  coping  with  carefully 
pointed  joints.  It  is  out  of  the  province  of  this  report  to 
discuss  the  various  details  of  design.  These  are  subjects 
with  which  the  architect  is  familiar.  However,  the 
accompanying  illustrations  show  that  these  necessary 
precautions  are  often  overlooked  and  neglected. 

In  an  article  entitled,  “Keeping  Buildings  Dry,’’  and 
in  regard  to  discoloration  on  the  underside  of  balconies, 
Cecil  Fidler,  Engineer  of  Standards,  Atlantic  Terra  Cotta 
Company  has  stated  as  follows : 

It  is  almost  impossible  to  make  the  deck  of  a  balcony 
watertight  by  means  of  a  cement  or  tile  finish.  A  cover¬ 
ing  of  sheet  metal  should  be  used  in  all  cases.  In  flashing 
the  tops  of  balcony  slabs  with  sheet  metal,  it  is  necessary 
to  run  the  flashing  out  to  the  nib  if  the  best  results  are 

to  be  obtained.  Quite  fre¬ 
quently  the  floor  of  a 
balcony  is  properly  flashed, 
but  the  flashing  terminates 
in  reglets  in  the  base  of 
the  balustrade.  This  prac¬ 
tice  almost  invariably  re¬ 
sults  in  the  saturation  of 
the  balcony  slab  by  water 
which  finds  its  way  in  at 
the  joints  in  the  balustrade 
and  runs  down  behind  and 
underneath  the  flashing.  By 
carrying  the  flashing  under¬ 
neath  the  base  course,  any 
water  that  enters  at  the 
joints  of  the  balustrade  can  not  penetrate  to  the  balcony 
slab,  and  the  soffit  of  the  balcony  is  kept  dry  and  unstained.’’ 

In  the  case  illustrated  in  FIGURE  23,  there  is  no  flashing 
at  all  on  the  balcony  below  which  the  efflorescence  ap¬ 
pears.  The  stonework  is  covered  by  large  copings  which 
communicate  directly  in  a  vertical  direction  with  that  part 
of  the  stonework  showing  the  efflorescence.  A  number 
of  the  vertical  joints  in  this  coping  have  partially  dis¬ 
integrated. 

Mr.  Fidler  further  recommends  the  complete  flashing 
of  the  washes  of  pediments  and  dormers  to  avoid  the  evils 
of  saturation  and  makes  the  statement: 

“While  the  use  of  sheet  metal  for  the  protection  of 
mortar  joints  may  entail  some  slight  additional  expense 
at  the  time  of  the  erection  of  the  building,  it  will  be  found 
more  economical  in  the  end  because  the  cost  of  mainte¬ 
nance  will  be  avoided.” 

Mortar  joints  often  not  water-tight 

It  became  apparent  during  the  field  study  that  architects 
and  builders  were  placing  too  much  reliance  on  the  mortar 
joints.  Close  inspection  of  many  cases  of  wet  walls 
showed  that  water  was  entering  the  mortar  joints  in  the 
wash  of  the  cornice  and  parapet  coping.  For  some  reason 
water-tight  joints  are  not  being  produced  by  caulking  and 


Figure  23.  The  stonework  below  the  balcony  is  not  protected 
by  flashing  and  shows  marked  efflorescence. 


18 


WET  WALLS  AND  EFFLORESCENCE 


Figure  24.  A  projecting  metal  flashing  with  drips  should  be 
placed  below  brick  sills  like  those  shown  here. 


Figure  25.  Joints  in  the  window  sills  have  cracked,  allowing 
excessive  moisture  to  enter  the  brickwork  below. 


grouting.  A  number  of  things  may  be  accountable  for 
this  condition  of  the  joints,  such  as  poor  workmanship, 
inferior  mortar  or  mortar  that  is  too  lean,  disintegration 
through  alternate  freezing  and  thawing  of  the  original 
moisture  introduced  during  construction  in  late  fall  or 
winter,  or  cracking  due  to  uneven  settlement  and  thermal 
expansion. 

Avoid  vertical  joints  exposed  to  excessive  moisture 

Vertical  joints  exposed  to  an  excessive  amount  of 
moisture  as  are  those  in  window  sills  should  be  avoided  as 
much  as  possible.  FIGURE  24  is  typical  of  what  will 
follow  if  this  precaution  is  not  observed.  This  wall  is  of 
sanddime  brick  and  efflorescence  is  noticeable  beneath 
the  rowlock  brick  sills  with  many  intervening  mortar 
joints  in  each  sill.  Of  course,  there  are  no  drips  on  such 
sills.  If  such  sills  must  be  used,  there  should  be  placed 
beneath  such  a  sill  a  suitable  metal  flashing,  projecting 
and  with  drips.  FIGURE  25  shows  a  church  whereon  crack' 
ing  and  initial  disintegration  of  joints,  especially  of  the 
vertical  ones,  has  occurred.  As  a  consequence  of  the 
failure  to  observe  these  precautions,  the  brick  above  the 
stone  belt  line  and  beneath  the  sills  are  here  being  exposed 
to  an  excessive  amount  of  moisture.  It  would  have  been 
better  had  the  sills  been  in  each  case  one  solid  piece  of  stone 
with  a  slope  to  the  wall  on  each  side.  Furthermore  such 
sills  (lug  sills)  should  project  at  least  two  inches  and  be 
provided  with  suitable  drips.  This  also  applies  to  the 
cornice. 

FIGURE  26  illustrates  protection  against  excessive  water 
penetration  at  the  sills.  Note  that  each  sill  is  a  single 
unit  and  not  two  or  three  units  with  intervening  vertical 
mortar  joints.  This  illustration  typifies  the  ideal  drainage 
for  sills.  There  are  good  drips  underneath  and  an  up' 
ward  slope  in  each  case  from  the  window  area  toward  the 
wall  to  left  and  right.  The  sills  also  project  more  than 
two  inches.  Good  cornice  and  well  pointed  joints  are 


also  characteristic  features  of  this  building.  Another 
model  of  good  design  is  illustrated  by  FIGURE  27.  Here 
there  are  good  drips  on  sills  which  are  single  units  with 
no  vertical  joints.  Other  desirable  features  are  the  wide 
eaves,  the  cornice  reentering,  protection  against  seepage 
at  the  base  by  having  the  brick  on  stone  some  distance 
from  the  soil  and  the  rain  water  leaders  extending  to  the 
ground  thus  avoiding  splashing. 

Projecting  courses  may  cause  ejflorescence 
Projecting  courses  of  brick  such  as  the  rowlock  or  soldier 
courses  apparently  intended  to  enhance  artistic  beauty  in 
a  wall,  in  reality  are  most  conducive  to  discoloration  as 
well  as  to  disintegration.  Where  such  courses  of  brick  are 
laid  in  a  wall,  there  should  be  ample  protection  against 
excessive  water  penetration.  The  vertical  courses  of 
brick  illustrated  in  FIGURE  28  are  being  exposed  to  exces' 
sive  moisture.  Efflorescence  will  inevitably  result  on  such 
exposed  areas  and  what  is  far  more  undesirable,  disintegra' 
tion  will  always  be  accelerated  when  mortar  joints  are  so 
exposed.  Note  in  this  instance  the  marked  efflorescence  on 


Figure  26.  Thi9  illustrates  good  drainage  for  sills,  with  adequate 
drips  and  the  proper  slopes  at  the  ends. 


WET  WALLS  AND 


EFFLORESCENCE 


19 


the  mortar  joints.  Lime  putty  mortar  was  used.  The 
combination,  poor  materials  together  with  poor  design 
from  the  standpoint  of  excessive  moisture  penetration, 
brings  about  condition  B,  the  most  undesirable  of  the 
four  mentioned.  In  this  particular  instance,  the  brick 
are  remarkably  free  from  efflorescence,  considering 
the  extent  of  exposure  to  which  they  have  been 
subjected.  In  time,  however,  the  soluble  salts  on  the 
joints  as  illustrated  may  be  carried  by  moisture  over 
the  face  brick,  and  one  who  observes  the  wall  then 
for  the  first  time  may  think  that  the  brick  are  directly 
responsible  for  the  efflorescence.  FIGURE  29  shows 
a  corbelled  area  on  a  new  building  that  is  dark  with 
moisture.  This  may  be  expected  eventually  to  result 
in  disintegration  of  joints  and  efflorescence  similar  to 
conditions  illustrated  in  FIGURE  33.  The  small 
recess  below  the  window  sill  collects  a  maximum  of 
water  for  the  vertical  joints  below. 


Figure  27.  This  building  illustrates  good  design  as  regards  sills,  wide 
eaves,  cornice  and  protection  at  the  base. 


Figure  28.  The  projecting  courses  of  brick  shown  here  receive 
excessive  moisture. 


Figure  29.  The  corbelled  area  is  dark  with  moisture,  and  as  the  build¬ 
ing  ages,  will  doubtless  show  efflorescence  and  disintegration  of  joints. 


In  the  design  of  all  walls  built  of  brick  some  consider' 
ation  should  be  given  to  protection  against  water 
penetration  rather  than  to  but  one  thing,  namely  artistic 
appearance.  To  corbel  out  with  one  or  more  courses  of 
brick  or  any  other  masonry  material,  is  always  a  dangerous 


procedure  unless  such  projecting  brick  courses  are  to  be 
so  situated  as  to  be  amply  protected  from  undue  exposure 
to  moisture  penetration. 

Protect  masonry  through  attention  to  design 
It  is  believed  that  a  realization  of  what  can  happen 
through  improper  design  will  go  farther  toward  cor' 
recting  this  evil  than  will  a  recital  of  a  large  number  of 
details  necessarily  involved  in  construction  planned 
to  protect  the  wall.  The  builder  is  familiar  with 
these  various  details  and  due  probably  to  the  fact 
that  he  relies  too  much  upon  the  weather  resistance 
properties  of  all  masonry  materials  he  too  frequently 
does  not  consider  the  possibility  of  modifying  the 
design  so  as  to  protect  them  more.  Such  an  example 
as  the  accompanying  illustration,  FIGURE  30, 
typifies  such  a  tendency  on  his  part.  Here  again 
are  the  maximum  number  of  exposed  vertical 
joints. 


Figure  30.  By  modification  of  design,  greater  protection  can  be  given 
masonry  materials  in  cases  like  this. 


20 


WET  WALLS  AND  EFFLORESCENCE 


Figure  31b.  In  retaining  walls,  the  exposure  is  especially  severe.  Even  well-burned  brick, 
such  as  were  used  here,  must  have  adequate  drainage  to  resist  frost  action. 


Figure  31c.  The  mortar  joints  in  this  wall  have  been  pointed  up  twice  and  need  attention  again. 
Direct  contact  with  moist  ground  at  the  back  of  the  wall,  without  insulation 
or  proper  drainage,  is  responsible  for  this  trouble. 


Walls  severely  exposed 

The  subject,  retaining  walls, 
is  interesting.  It  is  here  that 
masonry  materials  are  given  the 
most  severe  exposure  if  not  pro- 
perly  protected.  FIGURE  31b 
shows  a  coping  of  well  burned 
brick  on  a  retaining  wall.  Even 
well-burned  brick  or  other  good 
materials  must  have  sufficient 
drainage  if  they  are  to  resist  frost 
action.  The  result  here  is  due  to 
lack  of  proper  drainage.  FIG¬ 
URE  3  1  c  is  another  retaining 
wall  that  has  been  pointed  up 
twice  and  a  third  operation  of  the 
kind  is  in  need  of  being  done. 

FIGURE  3  Id  is  especially  inter¬ 
esting.  Below  each  disintegrated 
vertical  joint  in  the  cap  of  this 
wall,  there  is  a  crack  in  the  solid 
concrete  below.  Perhaps  no 
comments  on  FIGURE  31e  are 
required.  FIGURE  3 If  shows 
how  mortar  has  disintegrated 
under  a  cap  with  no  drip.  This 
is  also  part  of  a  retaining  wall. 

This  same  principle  applies  in  the  construction  of  chim¬ 
neys.  Chimneys  are  peculiarly  vulnerable  to  severe 
weathering  conditions.  The  accompanying  photograph, 
FIGURE  32  is  but  one  of  a  large  number  of  instances  of 
the  sort.  Here  again  too  much  dependence  was  placed  upon 
the  vertical  mortar  joints  in  the  brick  at  the  cap.  Such  a 
chimney  should  have  had  a  stone  cap  with  good  projection 
and  furnished  with  drips  of  wide  and  deep  grooves.  The 
thin  covering  of  stucco  in  this  case  has  not  endured  the  test. 

As  final  illustrations  of  a  combination  of  faulty  design, 


construction  and  maintenance,  FIGURES  33  and  34  should 
be  self-explanatory.  FIGURE  33  is  a  small  portion  of  the 
building  of  which  FIGURE  34  is  a  more  complete  view, 
not  however  showing  the  portion  shown  in  FIGURE  33. 
This  closeup  indicates  what  may  be  expected  in  years  to 
come  in  wall  areas  like  that  shown  in  FIGURE  29,  which 
is  on  a  new  building.  Corbelling  such  as  illustrated  in  these 
two  pictures  usually  leads  to  excessive  moisture  penetra¬ 
tion. 

In  FIGURE  33  it  may  be  noted  that  both  mortar  joints 


From  this  illustration  to  the 
next,  FIGURE  31a,  there  is 
added  the  further  undesirable 
condition,  soil  in  immediate 
contact  with  the  brick  in  the 
retaining  wall.  To  have  put  tar 
or  tar  paper  back  of  this  wall  or 
still  better  to  have  dug  a  trench 
back  of  this  wall,  lining  the 
trench  with  impervious  concrete 
and  then  to  have  filled  the  trench 
with  gravel  would  have  been  an 
additional  expense  well  worth 
while.  Within  a  short  time  it 
will  be  necessary  to  rebuild  this 
wall  and  this  procedure  will  cost 
considerably  more  than  would 
the  initial  precautions. 


Figure  31a.  Moisture  has  entered  this  wall  from  the  soil,  which  is  in  contact  with  the  brickwork. 


WET  WALLS  AND  EFFLORESCENCE 


21 


and  a  window  sill  are  disintegrating.  Repair  and  pointing  up 
are  badly  needed.  Leaking  downspouts,  defective  flashing 
both  at  the  chimney  base  and  in  the  parapet  walls,  project' 
ing  courses  of  brick  with  vertical  joints  exposed,  poorly 
designed  drips  on  sills  (such  being  too  shallow  and  so  close 


Figure  3  Id.  The  vertical  joints  in  the  coping  have  disintegrated, 
and  below  each  a  crack  has  formed  in  the  concrete. 


to  the  wall  as  to  be  ineffective),  the  sills  themselves  being 
of  soft  porous  sandstone  and  not  weather  resistant  and  the 
truncated  water  exit  (FIGURE  21,  same  building),  were 
the  immediate  causes  in  this  instance  of  the  efflorescence 
attended  by  disintegration. 


Figure  31e.  An  endless  number  of  retaining  walls  in  varying  stages 
of  failure  might  be  shown. 


Figure  3 If.  Under  this  cap,  which  has  no  drip,  the  mortar  has 
disintegrated  badly.  This  is  also 
part  of  a  retaining  wall. 


Figure  32.  Chimneys  receive  particularly  severe  exposure.  The 
vertical  mortar  joints  here  have  allowed  water  to  enter 
between  the  stucco  and  the  brick. 


Figure  33.  Corbelling  of  the  brick  is  the  chief  reason  for  the 
failure  at  the  right,  whereas  the  trouble  directly  under 
the  left  window  is  due  in  large  measure  to 
the  sill. 


Figure  34.  This  efflorescence  has  resulted  from  a  number 
of  clearly  recognizable  faults  of  design,  construction 
and  maintenance.  Figure  33  shows  a  closeup 
view  of  another  part  of  this  building. 


22 


WET  WALLS  AND  EFFLORESCENCE 


Again,  to  further  illustrate  combined  faulty 
design,  construction  and  maintenance,  com 
sider  FIGURES  35a,  35b,  35c  and  35d,  all 
pictures  of  the  same  building  although  parts  of 
an  adjacent  building  are  seen  in  FIGURES  35a 
and  35c.  This  was  originally  Condition  B, 
without  doubt.  Kiln  run  common  brick,  a 
portion  of  which  are  underburned,  compose 
the  wall.  FIGURE  35d  shows  the  extent  to 
which  these  brick  as  well  as  the  intervening 
mortar  joints  near  the  soil  have  disintegrated. 
Efflorescence,  very  noticeable  in  the  past,  is 
becoming  less  noticeable  at  present  while 
disintegration  progresses.  The  walls  have 
received  quantities  of  water  to  wash  out  the 
salts  for  the  most  part.  Galvanised  iron  which 
corrodes  comparatively  readily  was  used  for 
flashing  of  the  parapet  wall  which  is  about 
eight  feet  above  the  roof.  There  is  both 
seepage  and  splashing,  causing  saturation  of 
the  lower  wall.  The  coping  is  poorly  designed. 
There  are  downspouts  but  these  are  inside 
the  building  and  have  undoubtedly  become 
clogged.  As  a  result,  the  overflow  spouts 
have  been  called  on  to  do  the  work  with  the 
results  herein  illustrated.  As  the  joints  pn> 
gressively  disintegrate  the  degree  of  satura' 
tion  during  a  wet  season  increases.  Below 
the  wide  recesses  in  the  wall  are  projecting 
header  courses  of  brick.  It  would  be  difficult 
to  devise  a  more  favorable  condition  for 
entrapping  the  maximum  amount  of  moisture. 
Horizontal  exposures  are  here  unprotected 
by  either  sloping  or  by  drips. 


Figure  35a.  This  and  the  next  three  illustrations  all  show  parts  of  the 

same  building. 


Figure  35b.  The  walls  of  this  structure  are  composed  of  kiln  run  brick,  some 
of  which  are  underburned. 


Some  consideration  might  also  be  given 
finally  to  the  analogous  weathering  of  rock 
in  nature.  In  connection  with  the  following 
illustrations,  one  might  make  the  appropriate 
statement:  “Nature  destroys  her  own.”  In 
FIGURE  36a  can  be  seen  in  the  distance 
across  the  river,  the  result  of  frost  action,  sup' 
plemented  by  erosion  by  water  and  wind. 

FIGURES  36b,  36c,  and  36d  give  one  some 
notion  as  to  the  tremendous  forces  brought 
to  bear  in  repeated  freezing  and  thawing. 

Dynamite  could  hardly  do  more.  These 
stones,  of  course,  had  no  drips.  The  sand' 
stone  base  illustrated  in  FIGURE  37  is 
almost  as  much  at  the  mercy  of  the  elements. 

FIGURE  38  shows  a  bridge  railing  with' 
out  drip  or  enough  slope.  One  might  go  on 
indefinitely,  but  it  is  hoped  that  the  preceding 
illustrations  show  that  there  is  required  today  more  con'  salts  or  whether  such  salts  are  in  very  small  quantity  in 

sideration  of  the  subject,  water  penetration,  in  the  building  the  masonry.  Best  of  all,  there  will  also  result  far  less'  ten' 

industry.  Reduce  water  penetration  and  efflorescence  will  dency  toward  disintegration  and  this  after  all  is  a  far  more 
diminish  in  any  case,  whether  there  is  a  great  deal  of  soluble  serious  incident  than  is  efflorescence. 


Figure  35c. 


Disintegration  progresses  while  efflorescence  becomes  less  marked 
as  the  soluble  salts  are  washed  out. 


WET  WALLS  AND 


EFFLORESCENCE 


23 


Figure  35d.  This  closeup  reveals  the  extent  to  which  the  mortar 
joints  and  even  the  brick  have  disintegrated. 


Figure  36b.  Viewed  close  at  hand,  the  destruction  wrought  by 
repeated  freezing  and  thawing  is  seen  to  rival  the 
power  of  dynamite. 


Figure  36a.  Talus  slopes  such  as  this  are  common  sights  below 
cliffs  of  solid  rock,  along  shore  lines  everywhere,  for  frost  ac¬ 
tion  is  a  relentless  force,  initiating  the  process  of  disintegra¬ 
tion  and  opening  the  way  for  erosion  by  water  and  wind. 


Figure  36c.  Another  type  of  rock  broken  up  by  frost  action. 


Figure  37.  Moisture  penetrating  this  sandstone  base  has  begun 
its  powerful  disintegrating  action. 


Figure  36d.  Still  another  variety  disintegrated  by  frost. 


Figure  38.  This  bridge  railing  has  no  drips  and  too  little  slope 
to  dispose  of  the  water. 


24 


WET  WALLS  AND  EFFLORESCENCE 


Summary 


The  purpose  of  the  foregoing  is  to  point  out  the  fact 
that  in  the  main,  the  immediate  cause  of  efflorescence  and 
often  too  of  wall  disintegration  is  excessive  penetration 
of  moisture  into  the  wall.  The  field  work  supplemented 
the  fundamental  work  that  had  already  been  done  and 
that  had  established  the  fact  that  hardly  any  masonry 
material  is  exempt  from  the  possibility  of  containing  solu- 
ble  salts  in  quantity  such  that  it  may  under  favorable 
conditions  contribute  to  the  development  of  noticeable 
efflorescence.  The  favorable  conditions  are  wet  walls. 

With  but  one  or  two  definite  exceptions,  all  of  the  large 
number  of  instances  of  efflorescence  and  in  some  cases  wall 
disintegration  that  were  studied  could  have  been  prevented 
had  due  consideration  and  care  been  given  to  the  proper 
design,  construction  and  maintenance  of  these  buildings. 

A  few  examples  of  such  preventable  instances  of  efflores- 
cence  have  been  shown.  Some  details  in  way  of  design, 
construction  and  maintenance  which,  had  they  been  ob- 
served  and  remedied,  would  have  prevented  the  occur' 
rences  of  efflorescence  as  illustrated  by  photographs,  have 
been  mentioned.  There  are  many  more  of  such  details  and 
it  is  assumed  that  the  architect  and  builder  are  more 
familiar  with  them  than  is  any  one  else. 

Efflorescence  can  become  very  noticeable  on  the  wall  of 
a  building  composed  of  brick  or  other  masonry  materials 
that  are  exceptionally  low  in  soluble  salt  content  if  an 
excessive  amount  of  water  enters  that  wall. 


Any  efflorescence  appearing  on  the  wall  of  a  building 
that  is  suitably  designed,  constructed  and  kept  in  repair 
in  order  to  avoid  excessive  water  penetration,  will  be  due 
to  rare  and  abnormal  conditions.  It  will  in  time  gradually 
diminish  and  finally  disappear.  It  will  never  recur  under 
normal  conditions  even  though  the  soluble  salt  content  of 
the  entire  wall  be  higher  than  is  normally  the  case.  Pro- 
longed  and  heavy  wind-driven  rains  will  bring  out  efflores¬ 
cence  on  almost  any  wall,  but  this  efflorescence  is  of  the 
temporary  nature  described,  is  usually  of  short  duration, 
and  is  generally  unaccompanied  by  disintegration  of  joints. 

The  effort  on  the  part  of  manufacturers  of  face  brick 
to  develop  products  as  free  as  possible  from  soluble  salts 
(even  if  the  goal,  complete  elimination,  could  be  attained) 
will  not  in  itself  insure  against  the  development  of  efflores¬ 
cence  on  walls.  Their  work  must  be  supplemented  by  a 
concentrated  effort  on  the  part  of  architects,  builders  and 
owners  to  keep  the  walls  as  dry  as  possible.  It  is  also 
very  necessary  that  manufacturers  of  the  other  building 
materials  used  in  walls  with  the  face  brick  be  equally  con¬ 
cerned  with  the  question  of  soluble  salts  in  their  materials. 

Means  of  preventing  efflorescence  by  keeping  the  walls 
dry  have  been  outlined.  It  is  hoped  that  architects  and 
builders  generally  will  proceed  much  further  with  this 
study  and  that  the  face  brick  industry  will  have  their 
full  cooperation  in  keeping  dry  the  face  brick  walls  of 
buildings  yet  to  be  constructed. 


EFFLORESCENCE  ON  FACE  BRICK  WALLS 

(Publication  Approved  by  the  Director  of  the  Bureau  of  Standards  of  the  U.  S.  Department  of  Commerce) 


'  I  'HE  accumulation  of  salts,  usually  sulfates,  upon  the 
-L  outer  surface  of  the  wall  of  a  building,  is  commonly 
referred  to  as  “white  wash”  or  “efflorescence.”  These 
salts  may  exist  in  the  mortar  used  with  the  face  brick,  in 
the  face  brick  themselves,  and  usually  to  a  greater  extent 
in  the  softer  burned  brick  and  hollow  tile  backing.  They 
may  be  present  in  any  concrete  mortar  materials,  cement 
block,  etc.,  used  in  the  backing. 

Causes  of  efflorescence 

During  a  cool  and  humid  season  of  the  year  when  the 
wall  is  repeatedly  exposed  to  rain,  moisture  penetrates 
far  back  of  the  facing  and  takes  into  solution  some  of  these 
soluble  salts  from  both  the  back-up  and  the  facing  ma¬ 
terials.  As  soon  as  the  weather  becomes  favorable  for 
evaporation  of  this  accumulated  moisture,  as  in  the 
spring  of  the  year,  these  salts  are  carried  outward  and 
are  deposited  on  the  face  brick.  A  wall  under  process 
of  construction  is  particularly  apt  to  absorb  a  considerable 
amount  of  moisture.  Every  precaution  should  be  taken 


to  keep  an  unfinished  wall  covered  and  protected  from  rain 
or  snow  during  the  process  of  construction.  Moisture 
so  accumulated  in  the  wall  brings  the  salts  to  the  outer 
wall  surface  to  such  an  extent  that  the  efflorescence  be¬ 
comes  very  noticeable  before  the  building  is  even  com¬ 
pleted.  The  layman  who  sees  only  the  visible  salts  on 
the  outer  wall,  may  not  consider  any  of  the  materials  in 
the  wall,  beyond  what  he  actually  sees,  as  contributing 
factors. 

Purpose  of  investigation 

In  order  to  get  the  essential  facts  concerning  the 
mechanism  of  the  development  of  efflorescence,  the  Am¬ 
erican  Face  Brick  Association  conducted  an  investigation 
at  the  Bureau  of  Standards  in  accordance  with  that  insti¬ 
tution’s  Research  Associate  plan. 

Method  of  procedure 

To  obtain  information  concerning  the  development  of 
efflorescence,  it  was  thought  to  be  expedient  to  study 
primarily  the  materials,  brick  and  mortar.  Whatever 


WET  WALLS  AND  EFFLORESCENCE 


25 


facts  were  found  with  respect  to  intervening  cement  or 
lime  mortar  joints  in  the  outer  wall  of  face  brick  as  con' 
cerns  efflorescence  would  apply  to  such  lime  or  cement 
mortar  if  used  with  backup  materials,  provided  of  course 
that  water  could  penetrate  into  the  backing.  Whatever 
factors  there  are  in  plant  procedures  that  would  tend  to 
introduce  soluble  salts  in  face  brick  would  also  obtain 
in  the  process  of  manufacture  of  any  heavy  clay  product 
manufactured  under  similar  conditions. 

In  order  to  study  the  parts  that  mortar  materials  as 
well  as  face  brick  play  in  the  development  of  efflorescence 
on  a  wall,  there  were  selected  for  the  purpose  four  types 
each  of  well  known  and  extensively  used  limes,  portland 
cements  and  bricklayers’  cements.  There  were  also 
selected  from  various  parts  of  the  United  States  fiftyffive 
different  types  of  face  brick. 

The  brick  and  mortar  materials  were  used  in  test 
panels  made  as  follows :  three  brick  of  the  same  type  were 
laid  up,  one  above  another,  with  intervening  joints  of  a 
mortar  prepared  from  one  volume  of  lime  or  cement  mixed 
with  three  volumes  of  Standard  Ottawa  Sand.  The 
mortar  joints  were  approximately  ffff  inch  in  thickness. 

Two  such  panels  were  constructed  with  each  type  of 
brick  laid  up  with  a  given  lime,  portland  cement  or  brick' 
layers’  cement  mortar.  Each  pair  of  panels  constituted 
a  single  test.  Twelve  tests  of  twenty  Tour  panels  were 
made  with  each  of  the  four  limes  and  cements,  thus  bring' 
ing  the  total  number  of  panels  tested  to  288. 

After  the  panels  were  constructed  they  were  allowed 
to  set  and  dry  on  the  floor  of  the  laboratory  before  being 
subjected  to  the  test  for  efflorescence.  At  the  end  of  three 
weeks,  each  pair  of  panels  was  set  in  a  separate  pan  con' 
taining  about  one  inch  of  distilled  water,  one  panel  of 
each  pair  being  set  vertically  and  the  other  horizontally. 
Water  was  added  to  the  pans  from  time  to  time  as  required 
to  replenish  loss  by  evaporation.  The  tests  were  con' 
tinued  for  a  period  of  six  months. 

Simultaneously  with  these  panel  tests  individual  tests 
for  efflorescence  were  made  with  the  brick  of  the  same 
types  as  those  used  in  the  panels.  Each  lot  of  six  brick 
representing  one  manufacturer’s  product  was  tested  in  a 
pan  separate  from  the  others.  The  brick  were  set  ver' 
tically  in  the  pan  and  in  about  an  inch  of  distilled  water 
and  the  tests  in  all  cases  were  continued  for  a  period  of 
six  months. 

Results  of  tests  for  efflorescence 

It  must  be  realized  that  the  tests  above  described  were 
such  as  to  provide  conditions  most  favorable  for  the  de' 
velopment  of  efflorescence.  If  the  same  brick  and  inter' 
vening  mortar  joints  had  been  placed  in  the  outer  wall  of 
a  building,  rainfall  from  time  to  time  would  have  tended 
to  wash  off  the  deposits  of  salts  on  the  surface.  However, 
in  this  case  there  was  in  each  individual  test  a  steady 
accumulation  of  such  salts  on  the  dry  portions  of  the 
panels  and  no  removal  of  accumulated  salts  during  the 


six  months’  period  of  the  tests. 

The  total  number  of  different  types  of  face  brick  used 
in  the  panels  was  thirty'two.  Of  this  number  fifteen  did 
and  seventeen  did  not  develop  any  noticeable  efflorescence 
during  the  six  months’  tests  made  on  the  individual  brick 
themselves  and  not  in  contact  with  any  mortar.  The 
seventeen  types  which  did  not  develop  any  efflorescence 
when  so  tested  individually  did  develop  noticeable 
efflorescence  with  at  least  one  of  the  various  types  of 
mortars.  Both  the  face  brick  and  the  cements  and  limes 
used  in  these  tests  were  so  chosen  as  to  be  as  nearly 
representative  as  possible  of  such  building  materials  as 
used  in  the  United  States.  The  results  should  therefore 
be  very  indicative  of  the  contribution  that  each  material 
would  make  toward  the  development  of  efflorescence  on 
a  wall. 

The  tests  were  rigorous  and  extended  over  a  compara' 
tively  long  period  of  time.  The  gradually  accumulating 
salts  on  the  dry  surfaces  of  the  panels  or  of  the  individual 
brick  were  not  removed  by  rain,  a  condition  which  obtains 
when  such  materials  are  used  in  the  wall  of  a  building. 
In  view  of  the  fact  that  iff  or  fifty'three  per  cent  of  the 
types  of  face  brick  developed  no  efflorescence  during  the 
six  months  when  tested  individually  (even  though  the 
tests  were  much  more  severe  than  any  actual  conditions 
existing  in  the  wall),  but  did  develop  noticeable  efflores' 
cence  when  laid  up  with  at  least  one  type  of  mortar,  it 
must  be  concluded  that  the  face  brick  manufacturers  have 
to  a  considerable  extent  reduced  any  tendency  on  the 
part  of  their  product  to  develop  efflorescence. 

Methods  of  reducing  the  extent  to  which  lime  and  cement 
materials  may  contribute  to  efflorescence 

Theoretically,  any  possible  contribution  to  wall  efflores' 
cence  on  the  part  of  mortar  materials  may  be  prevented 
or  decreased  if  the  mortar  could  be  rendered  more  im' 
permeable  to  water.  It  is  not  possible  to  fill  all  of  the 
voids,  but  it  is  possible  that  the  presence  of  a  certain 
substance  or  substances  introduced  into  such  voids  could 
lessen  the  passage  of  water  due  to  capillarity.  It  is  rea' 
sonable  to  assume  that  if  little  or  no  water  can  enter 
mortar  materials,  there  can  be  no  leaching  out  to  any 
appreciable  extent  of  any  salts  which  they  contain. 

Experimental 

A  relatively  soft  and  porous  type  of  brick  was  used 
throughout  in  all  of  the  tests  of  mortars  containing  the 
water  repellent  substances.  Excepting  those  tests  where' 
in  a  cement  was  used  which  already  contained  the  water 
repellent  substance,  the  mortars  were  made  either  with 
portland  cement  or  lime,  or  mixtures  of  lime  and  cement, 
together  with  sand.  The  relative  proportions  of  the 
mortar  materials  were  such  that  the  volume  ratio  of  cement 
or  of  lime,  or  of  the  lime  plus  cement  (if  mixtures  were 
used),  to  sand  was  one  to  three.  Excepting  those  trials 
made  wherein  a  cement  was  used  to  which  the  water 


26 


WET  WALLS  AND  EFFLORESCENCE 


repellent  material  had  already  been  added  at  the  factory 
and  excepting  also  those  trials  in  which  diatomaceous 
earth  was  substituted  in  part  for  sand,  the  amount  of  the 
water  repellent  substance  used  was  either  that  as  sped' 
fied  by  the  manufacturer,  if  it  had  been  purchased  on  the 
market,  or  else  (if  it  were  not  a  material  made  solely  for 
this  purpose)  an  amount  of  it  equal  to  two  per  cent  by 
weight  of  the  cement  or  of  the  lime  or  of  the  lime  plus  the 
cement  was  used. 

The  water  repellent  materials  were  added  directly  to 
the  mortar  materials  at  the  time  of  mixing.  Distilled 
water  was  used  in  such  quantities  that  upon  thorough 
mixing,  the  mortar  had  the  desired  consistency  and  was 
thoroughly  workable. 

Six  brick  laid  up  with  the  mortar,  giving  five  mortar 
joints,  constituted  a  panel.  After  being  constructed, 
the  panel  was  allowed  to  set  and  dry  on  the  laboratory 
floor  for  a  period  of  three  weeks  prior  to  beginning  the 
test.  After  this  length  of  time,  the  panel  was  set  (brick 
flatwise)  in  a  shallow  pan,  the  joints  being  parallel  to  the 
base  of  the  pan.  The  lower  brick  was  about  half  sub' 
merged  in  a  saturated  solution  of  sodium  sulfate  which 
was  poured  into  the  pan  upon  beginning  the  test.  For 
a  period  of  six  months  the  level  of  the  solution  of  sodium 
sulfate  was  kept  fairly  constant  and  observations  were 
taken  from  time  to  time,  noting  any  upward  progress  of 
the  salt  solution  through  the  mortar  joints.  When  pene' 
tration  did  occur,  the  crystals  of  sodium  sulfate  appeared 
upon  the  second,  third,  etc.,  brick  from  the  bottom 
according  as  the  rate  of  penetration  was  slow  or  rapid. 
The  test  was  continued  over  a  period  of  six  months. 

Results  of  tests  on  water  repellent  materials 

For  the  most  part,  all  of  the  compounds  used  tended 
to  decrease  the  rate  of  penetration  of  the  salt  solution 
through  the  mortar  joints.  The  inert  materials,  clay 
and  diatomaceous  earth  did  not  entirely  prevent  penetra' 
tion  in  all  cases,  but  were,  however,  more  or  less  effective. 
Ammonium,  aluminum,  and  calcium  stearate  were  equally 
effective  and  no  salts  penetrated  beyond  the  first  mortar 
joints  in  any  panel  in  which  any  one  of  these  substances 
was  used. 

A  wall  in  which  these  water  repellent  substances  have 
been  used  must  not  be  considered  as  being  thoroughly 
waterproof.  Rain  may  penetrate  through  face  brick  to 
the  backup  materials,  take  salts  in  these  materials  into 
solution  and  then  carry  them  back  to  the  outer  wall  dun 
ing  the  subsequent  process  of  the  drying  of  the  wall. 
The  purpose  of  the  stearates  is  only  to  render  less  likely 
the  contributing  of  the  various  mortar  materials  used  in 
the  entire  wall  to  the  development  of  efflorescence  on  the 
outer  wall.  Furthermore  it  is  evident  that  in  order  for 
this  condition  to  be  realized,  the  water  repellent  substances 


must  be  used  in  all  of  the  mortar  in  the  wall,  in  the  backing 
as  well  as  in  the  mortar  used  with  the  face  brick. 

Other  means  of  reducing  efflorescence 

Since  two  conditions  must  exist  for  efflorescence  to 
appear  on  the  outer  wall,  it  is  obvious  that  there  are  two 
means  of  reducing  efflorescence.  One  of  these  conditions 
is  the  presence  of  salts  in  the  materials  in  the  wall,  from 
front  to  back.  The  other  condition  is  the  penetration  of 
moisture  into  the  wall,  taking  these  salts  into  solution. 
The  manufacturer  should  concern  himself  with  the  first 
condition  mentioned.  The  architect  and  builder  can 
relieve  the  second,  penetration  of  water  into  the  wall,  to 
some  extent  at  least. 

The  use  of  the  stearates  as  watenrepellent  substances  in 
the  mortar  is  suggested.  In  addition  to  this,  careful  and 
prompt  pointing  and  waterproofing  of  parapet  walls, 
copings,  etc.,  and  flashing  to  prevent  the  penetration  of 
water  into  the  walls  will  also  help.  In  the  case  of  parapet 
walls,  it  is  well  to  carry  the  flashing  completely  through 
the  wall  at  one  or  two  courses  above  the  roof  level.  The 
parapet  wall  is  then  completely  separated  by  an  impervious 
membrane  from  the  other  portion  of  the  wall  and  conse' 
quently  water  can  not  penetrate  down  into  the  wall  and 
later  be  drawn  up  to  the  top  of  the  parapet  by  capillarity. 
Architects  should  seek  still  further  to  avoid  trouble  by 
waterproofing  the  entire  inner  side  of  the  wall  and  should 
use  impervious  coping  with  carefully  pointed  joints. 

The  manufacturers  of  face  brick  are  able  to  reduce  to  a 
negligible  quantity  soluble  salts  in  their  product,  chiefly 
by  means  of  special  burning  procedures.  Often,  also, 
they  have  made  use  of  barium  compounds,  adding  them 
to  the  clay  to  render  the  sulfates  insoluble.  To  a  lesser 
degree,  perhaps,  such  measures  can  be  used  in  the  manu' 
facture  of  the  clay  products  used  as  back'up  materials, 
although  the  selling  price  of  such  products  does  not  war' 
rant  the  application  of  the  comparatively  expensive  mea' 
sures  as  used  in  the  manufacture  of  face  brick  to  eliminate 
any  soluble  salts. 

The  builder  who  would  guard  especially  against  the 
occurrence  of  efflorescence  on  the  outer  wall  should  take 
into  consideration  each  and  every  material  that  is  to  com' 
pose  the  entire  wall.  If  any  tests  are  to  be  made  to  de' 
termine  the  presence  of  soluble  salts,  every  material  in 
the  wall  should  be  so  tested  and  it  is  equally  important 
that  every  necessary  precaution  be  taken  to  reduce  pene' 
tration  of  water  into  the  wall  to  a  minimum. 

A  more  detailed  report  covering  the  work  done  has  been 
published  by  the  Bureau  of  Standards  as  Technologic 
Paper  No.  370,  under  the  title  “Cause  and  Prevention  of 
Kiln  and  Dry'House  Scum  and  of  Efflorescence  on  Face 
Brick  Walls.” 


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